right now, the leagues are 15/15. I don't think they do interleague, so that means an idle team every night like it was in MLB before the Astros move. Why not go 16/14 and buy/move Vegas? If no one really wants to be there, then you'd think moving it might be possible. Why not a straight swap of Richmond and Vegas? Is there an AA league Vegas (Former Richmond) could join?
They're 16/14 at present, and there's no AA anywhere close to Vegas - as in, the closest team is Midland, which is almost exactly 800 miles away. That's a total non-starter. A buy/move of Vegas might work, but you'd need to swap the 16/14 the other way and find a landing city. Best candidates to be the second team to move to the IL from the PCL would be Nashville.
Of course, my preferred solution would be to move the Orioles to Vegas and move the Nats AAA to Baltimore, but Donald Trump will have a normal haircut and Stevie Wonder will be a pilot before that happens.
Is there anything stopping them from setting up Richmond as an expansion team?
Yes. There are already 30 AAA teams. There can't be more AAA teams than major league teams. That and there's already a AA team in Richmond that occupies the only viable stadium and is signed through 2020 with the Giants.
You'd think they could split a stadium with UVa. how big is UVa's stadium? Are they looking for an upgrade?
It's a tad over 5,000 right now, and it's actually being renovated and expanded right now (as in, it's under construction right now). Capacity will increase modestly, but not up to AAA size. It's also owned by UVA, and Charlottesville really isn't an ideal option for a minor league team - virtually the entire season happens when the city is missing 20,000 people or so. A-ball maybe - but again, you'd need to cut a deal with UVA to use Davenport, which would be fantastic by the standards of the Carolina League.