College hockey is an odd thing compared to other NCAA sports. For hockey, most of the top players will play Tier I or Tier II juniors (under 21 league) for two years after high school. This is where NCAA teams recruit from. Tier III junior hockey is weak, and only a handful go to NCAA from that level, while several will go to ACHA D1 schools. That's why the freshman on the West Point and Air Force hockey teams are 21. It's almost impossible to play Tier I or Tier II juniors and go to college at the same time. Not only is it tough to fit enough classes in on Monday through Thursdays with mid-day practices, but there is a chance you can get traded to another team in another city. Frankly, I'm not sure how those players would get through admissions after being out of high school for two years with little/no college experience, but West Point and Air Force seem to get it done. But USNA's ACHA D1 hockey is pretty close to NCAA D3 hockey, so it's good hockey and fun to watch. Their home games are posted on Youtube.
Another thing to consider, as another poster pointed out, teams in ACHA are able to avoid Title IX issues, since it's a club sport in that league. I think the only issue with the seating capacity of the arena is that it needs to have enough seats to sell to support the program at the NCAA level (admittedly, I'm really not sure what that means for USNA). I may be wrong, but I don't think the NCAA has a stadium size requirement. West Point has a sizable arena that holds around 2,500, compared to USNA holding around 700. I haven't been inside the arena, so I don't know how much additional seating you can get from expanding the bleachers. Robert Morris (NCAA D1) has a small arena with about 1,500 seats. I'm sure USNA could rebuild the bleachers to support that level inside the arena.