As a vehicle maker, I mostly just make whatever I think would be fun to play. That's why after a while of making WWII tanks I realized that most of them were the same and then I turned to making fictional tanks and such.
Honestly, I'd like a return to the RTB period when people didn't concentrate on making giant packs of the same stuff and just made one or two really eccentric and fun vehicles. I think that somehow the add-on community, myself included, has shifted more towards the looks of what we make rather than the gameplay aspect, at least as far as vehicles are concerned.