I don't see 3 vs. 4 guards as a tough decision at all. The reason I say that is we all know we have talent and depth at every position. We can put a potential AA candidate at the 4 playing her natural position, with a backup that could be a sixth women of the year in many conferences. That is just Aaliyah and Aubrey, not even figuring any potential contribution from Mir, or Dorka or Amari playing some 4.
Is it a crowded numbers game at the guards too? Of course ,it is at every single position on the team. So why do we have to try to fit a square peg in a round hole? They may be great square pegs, but every one of the potential 4th guards at the 4 would be more effective at their more natural position.
For that matter the same principle applies to our undersized but very athletic 4's namely Aubrey and Mir. I am pretty sure they could easily play the 3 defensively, and in rare end of period defensive lineups maybe they could be used there for a possession, but for the most part we shouldn't be trying to figure out more ways to get them minutes at the wing either.
Evina is the most capable of the guards of "approximating" a 4, and her versatility (swiss army knife) is tremendous, but remember her first two years she was a point guard. Christyn and Azzi are natural 2's, and I would argue they would be slightly less effective as a 3, and much less effective battling bigs at the 4. The closest thing to a natural 3 on the roster by position might be Caroline, who will probably be fighting for limited minutes as a backup there.
If all of the players were new to the team, I don't think think we would be having much of the 3 vs. 4 guard debate. The debate is elevated because of having all our returning starters coming back, and three seniors among them. Demoting a very good starter, particularly a senior, is something some on the Boneyard would not want to do, or think is appropriate, even if the challenger was better.
I have no idea how Geno will react. If he defers to the returning starters and seniors he could keep the returning starters and a four guard lineup. If he picks the best player for each position, I think it is far more likely he goes with 3 guards, and a senior starter is benched. Regardless I think the burden of proof will be on the challengers. They probably have to clearly beat out a returning starter for Geno to make a change.