Actually, I've noticed a general inclination in commentaries to see this 'prince' as functionally superior to the pre-exilic kings.
One author that I think summarizes this perspective especially well is Iain M. Duguid,1 who emphasizes the increase in the prince's duties as leader of Israel.
It is thus already clear that we have to do with an exalted figure, far greater than any nāśî' of the period of the Hexateuch and more akin to the pre-exilic kings. This picture is further defined, both positively and negatively, in the allocation of the land. Negatively, the Temple is no longer to be simply part of a larger palace complex, as Solomon's Temple had been (Ezek. 43:8): instead it will be surrounded by a priestly area to avoid all danger of defilement. Further the city is no longer the king's private preserve, as was Jerusalem ("the City of David"): the new city will belong to the whole house of Israel (Ezek. 45:6; 48.19). Positively, however, the nāśî' is allocated a large portion of land within the consecrated area (terûmâ), closer to the Temple than anyone else except the priests and Levites. This is a gracious gift indeed, considering the past history of the former kings.
Duguid does give an explanation for the separation of the temple from the royal palace, and the explicit limitation of land for the prince: it is to 'prevent the abuses' Ezekiel mentions of earlier kings, so the prince 'will not be tempted'.
But then Duguid immediately goes on to highlight the things that distinguish Ezekiel's prince from earlier kings of Israel, namely the prince's direct involvement in the religious practices as the nation's representative:
- The prince is permitted 'to eat bread in the presence of the Lord inside the closed east gate of the Temple'; this is 'especially holy because the Lord has passed through [the east gate]'
- The prince gathers gifts from the people to give to the temple on their behalf
- The prince provides the grain offering, sin offering, burnt offering, and fellowship offering on the whole kingdom's behalf, 'to make atonement for the house of Israel'
- The prince is permitted to come to the threshold of the temple, in contrast to the rest of the people, who would be required to stop sooner (Duguid estimates about ninety feet)
After going through each of these in detail, Duguid makes an important note:
So great is the nāśî''s involvement with the cult that some scholars have seen him as a purely sacral figure, a "Kirchenpatron". But this fails to take account of the essentially Temple-centred nation of Ezekiel 40-48. Everything is viewed from a cultic perspective. If the nāśî' is portrayed as a purely sacral figure, then so also is the entire congregation. They too have no non-cultic tasks described, except perhaps for those who are fishing in the transformed Dead Sea (Ezek. 47:10)! Omission does not imply annulment: Ezekiel is highly selective in what he discusses. Therefore, in considering the limitations which Ezekiel places upon the nāśî', it is necessary to pay attention to what is said rather than what is not said.
In other words, to say the prince is less important for Israel than the pre-exilic kings is primarily an argument from silence, in Duguid's perspective. Ezekiel 40-48 is focused primarily on a restored temple system, so what Ezekiel has to say about the prince is in the specific context of that temple; chapters 40-48 are not necessarily an exhaustive description of all of the prince's responsibilities as the 'king' and 'shepherd' of Israel.
1 Iain M. Duguid, Ezekiel and the Leaders of Israel, p.50-53