I have been thinking about this for ages, sorry if it has been suggested before but I can't find it so;
Thanks to the ingenious new vehicle ownership system, I don't see any reason why a player can't own more than one vehicle, say 2 or 3 should be enough.
Owning a plane is great, but I miss my wheels, and I sure don't want to sell up to get them back, and when I was saving for my plane I really enjoyed owning some of the cheap vehicles that have a lot of character, like the boxville, greenwood or golfcart etc. Owning a bike and a car would also be useful, not to mention that almost nobody buys a boat for obvious reasons, but if we could own 2 or 3 vehicles (or more) you might see a bit more traffic on the water, which would be fun in my opinion.