At my university our minyan davens nusach Ashkenaz. Recently some have expressed the desire to allow the shatz to daven nusach Sefard, under the logic that since there are basically no permanent members of the minyan (since we all graduate eventually), maybe we don't have a minhag hamakom. Is that a valid argument?
The following is admittedly a weak and Aggadic answer. I've got a hammer, and if you squint right at this question, it looks kinda like a nail. I strongly suspect that a better answer could be found in actual Halachic sources.
An essential difference between a community and an individual is that the community is "eternal," while individuals' lives are finite. This comes up, for example, in R' Hirsch's commentary on "Barechu" in his Siddur. He points out that we require a minyan, the smallest unit that can be called a community, to say "Blessed is the Lord, the Blessed One forever and ever," since the Jewish People (as represented by this community) can pledge to keep blessing God forever, while finite individuals cannot.
By that standard, no individual members of any community are permanent, and yet "permanent" communities persist. From the point of view of "eternity," it's hard to tell the difference between four years (or five or six or "oy, I've got to finish this dissertation already!") and 120.