Sounds like the solution to this is something akin to WN's system where drinks are brought by hand and there are no carts whatsoever. Perhaps in combination with a VX-style ordering system there would be no need for carts at all.

Worst I experienced on AS was a Hawaii flight in Y on a plane with only 2 lavs in back - the line was 10 people deep the entire flight. (I'm pretty sure it was a flight to HI...could've been a transcon).