The main reason you'd want to play Vegeta in DBFZ is his Assist. This thing is stupid good and it does everything you could ever want or need. His assist will pretty much synergise with anybody, given the sheer, unadulterated versatility it brings to the table. As such, you don't really need to build a team around him.
Vegeta is rock solid no matter where he goes on your team, even here. He has a strong grip on neutral and his mixups after 236L are pretty good when covered by assists. His assist is what prevents most people from playing him point, but it's certainly possible to play him here and succeed.
Vegeta is always doing good as long as he's not point. Between his amazing assist's power to extend combos, secure blockstrings and flexibility, Vegeta will always be useful.
Same as Mid. Put Vegeta in the position that suits your team composition better.
Literally pick whoever you want. He's THAT versatile, and being a big softy at heart means that he'll always fit in any team, as long as everyone's in a good position.
Tips and Tricks
Fighting SS Vegeta