I really want to see someone from 2220 post here--
their drive train was one of a few that I hadn't seen before this year.
As for 2667, we were terribly vanilla. We did pretty much what the OP did, but got wider wheels from Fleet Farm and used some 3D-printed parts to hold the pulleys to the wheels. Surprisingly we had zero failures at our regional and on our practice bot, even though we were using PLA at like 40% fill.