I think Tien's transformation should be like Krillin's. Just a change in looks. His main form could be his green outfit, while his second form could be his buu saga outfit. He'd get a big power boost too, but he'd only have that one form. This would be the easiest way to do it.
The harder way would be to include a buddy, which I think should be Yamcha because he'd have different attacks and would be unique. Chiouzu would just be a weaker copy of Tien. All 3 together would be nice too. But keep in mind..we'd have to model, make sprites for, and animate all 3 characters. So its really up to the modelers what they want to do. I'll still do sprites either way.