I will not specifically reference spelling differences, since names in Scripture often bear different spellings. While such could indicate a different person, it need not, so spelling difference alone is not enough to make a judgment one way or another about who the referent is.
Regarding Daniel's Reputation
Yes, Daniel was young. But if one follows the timeline of Daniel, he increased in reputation at a rapid pace.
- 605 BC he is taken into captivity; almost instantly upon his arrival in Babylon, he already makes a righteous name for himself in his unwillingness to defile himself with the king's meat (Dan 1:8) during his three year training period (Dan 1:5).
- 602 BC would end the three year training period (Dan 1:18), at which time Daniel and his friends stood out from the crowd, even to King Nebuchadnezzar (Dan 1:20).
- Later 602 BC—it is likely in same year1—Daniel also makes a further righteous name for himself in interpreting Nebuchadnezzar's dream (Daniel 2), righteously saving a number of innocent wise men from the king's death sentence (innocent in the sense that the king expected men to be able to tell him the content of his dream, which no person can do of himself [Dan 2:28-30], so they were being put to death for an unreasonable request). Daniel's popularity would have skyrocketed in Israelite circles as they learned of the king's reaction (Dan 2:46) and his promotion of Daniel (Dan 2:48) to highest of the wise men in the realm.
Daniel is not present in the events of chapter 3, and chapter 4 is of uncertain dating (none given in Scripture). While chapter 4 events may have increased Daniel's reputation, including his righteous call to the king turning to righteousness (4:26), neither this event or the later visions Daniel has during the reigns of later kings are needed, for the points above already established Daniel's reputation prior to Ezekiel even arriving in captivity himself during the second deportation (597 BC), much less the timing of his vision (sometime within or after the 6th month of the 6th year of his own captivity, per Ezek 8:1, but before the 5th month of the 7th year of his captivity [Ezek 20:1]).
This places Ezekiel 14:14 somewhere around 591-590 BC, roughly 11-12 years since Daniel's reputation was solidified by the events of Daniel chapters 1-2. Ample time to be referring to Daniel of the Book of Daniel.
Who is Making the Reference?
Yes, Ezekiel is the attributed human author of the book bearing his name, and with this I agree. But what is stated in Ezekiel 14:12 is that "the LORD came again to me, saying..." (NKJV), of which 14:14 is part of what was stated by YHWH, as the end of v.14 restates, "...says the Lord GOD." So the question is, would YHWH be referencing someone other than Daniel of the scriptures to indicate righteousness to the Israelite people? To this, I would have to answer "no," as it would make no sense in the historical context to reference anyone other than the most recent "hero" (so to speak) of righteousness in Israelite eyes.
It is actually this last point, perhaps, that is why Daniel fits between Noah and Job. Sometimes the central position is a point of emphasis (such as in chiastic structures in Hebrew).
The contemporary Daniel fits contextually with these two men like so:
All are Righteous Intercessors/Deliverers: Noah and Job interceded for their families (Noah with the Ark construction, Gen 6:13-22, as it was he that was viewed as righteous; Job with his sacrifice for his children's possible sin, Job 1:5). Daniel just recently helped deliver his three friends by leading the dietary protest and then delivering the wise men of Babylon from death, including the Israelite ones that just came through the three year training (Daniel's brethren, at least in the broad sense—we do not know if he had any actual family with him).
All were Righteous Men Geographically Dissociated with the Land of Israel Now: The fact that Noah and Job were not Israelites is not what is relevant. Daniel was no longer in "the land" of Israel (and thus, not in Jerusalem that was going to be judged, v.21), while Noah and Job also were not in the land of Israel (whether they never were present in the land area that would become Israel is unknown). These three that have point #1 in common are being hypothetically placed into the land for purposes of the illustration, to demonstrate that if any one of them were to be there during the coming judgment, they could not have interceded to deliver anyone; he alone (whichever one) would be all that one's righteous intercession could deliver during the coming judgment upon Jerusalem (v.21).
Likely as well, precisely because Daniel worked as a non-explicit deliverer (i.e. not delivering just his family) that he also fits central to the group. He was the one who delivered his people (the wise Israelites) and those not his people (the Babylonian wise men) from death. The illustration in Ezekiel is that no one from the land—family or otherwise—will be delivered because of the righteousness of another.
Daniel is the newbie to the "righteousness" scene compared to Noah or Job, but at the time of Ezekiel's vision, he is very much at the center of both Israelite and Babylonian interest. This popularity along with his fitting the pattern needed for the illustration with Noah and Job argues in favor of the contemporary Daniel being included in the group.
1 Stephen R. Miller in Daniel, Vol. 18, The New American Commentary (Nashville: Broadman & Holman Publishers, 1994), pages 76-77, addresses the dating of the events in chapter 2 from those of chapter 1 (NOTE: His footnotes have been replaced by letters here to keep them separate from this answer's footnotes):
2:1 Nebuchadnezzar had this dream in his “second year,” which
according to the Babylonian calendar (likely followed by Daniel in
dating the Babylonian kings) would have extended from Nisan
(Mar.–Apr.) 603 to Nisan 602 B.C.[a] A pertinent question is, Had Daniel
completed the three-year training program spoken of in 1:5? Wood
thinks that Daniel and his friends had not and argues that this is the
reason they were not called before the king with the other wise men.[b]
Most naturally the text is taken to mean that the Hebrews had finished
the program, that is, the events of chap. 2 follow chronologically the
interview at the end of the training program described in chap. 1.
Moreover, in 2:48 Daniel is made chief wise man by the king,
indicating that he had finished his training and already was
classified as part of this group.
Yet how could Daniel have finished a
three-year training program by Nebuchadnezzar’s second year if he was
captured in the year in which Nebuchadnezzar became king (605 B.C.)?
Driver explains the three years on the basis of the accession year
reckoning employed in Babylon and Judah.[c] By this method the time until
the first Nisan (Mar.–Apr.) is considered the accession year of the
king, not his first year (see chart).
Years of Training Year of King’s Reign Date
First Accession year From Sept. 605
(the time Nebuchadnezzar
to Nisan (Mar.–Apr.) 604 B.C.
Second First year Nisan 604–603 B.C.
Third Second year Nisan 603–602 B.C.
Nebuchadnezzar’s second year did not end until April 9, 602
B.C.,[d] and Daniel was taken into captivity almost three full years
earlier in the summer of 605 B.C. Driver also points out that Daniel
did not have to train three complete years, but according to Hebrew
usage, a part of a year was reckoned as a whole.[e] This would mean that
the program could have lasted less than two years if it consisted of a
full year and parts of two others. Any of these suggestions (or a
combination of them) could explain how the three-year training program
was completed in Nebuchadnezzar’s second year.[f]
[a] If Daniel employed the Judean calendar, as he did in dating the Hebrew king Jehoiakim (1:1), Nebuchadnezzar’s second year would be from Tishri (Sept.–Oct.) 604 B.C. to Tishri 603 B.C. Since Nebuchadnezzar was not a Judean king, Daniel probably dated the Babylonian monarch by his own system.
[b] L. Wood, A Commentary on Daniel (Grand Rapids: Zondervan, 1973), 49–50.
[c] S. R. Driver, The Book of Daniel, CBSC (Cambridge: University Press, 1922), 17. Also E. J. Young, The Prophecy of Daniel (Grand Rapids: Eerdmans, 1949), 55–56; G. L. Archer, Jr., “Daniel,” EBC (Grand Rapids: Zondervan, 1985), 41–42.
[d] J. C. Whitcomb, Daniel (Chicago: Moody, 1985), 29.
[e] Driver, Daniel, 17; cf. Young, Prophecy of Daniel, 56; J. G. Baldwin, Daniel, TOTC (Downers Grove: InterVarsity, 1978), 85.
[f] For other explanations see J. A. Montgomery, A Critical and Exegetical Commentary on the Book of Daniel, ICC (Edinburgh: T & T Clark, 1979), 140–41.