Pick a property and pick a gameplay style you'd love to see for a new fighting! Or just kinda create something out of your own imagination, though at least try to keep in mind a media property of some sort.
One thing that I feel Dragon Ball misses a lot, is quality fighting gameplay. There have been proper fighting games over the years, I think a number of the older sprite based ones played like regular fighters, but it's been a long time since DB has had good fighting in it, as Xenoverse certainly doesn't have that.
I'd personally want to see a game that encompasses Dragon Ball, Z, GT, and Super, but done in a Capcom fighting game style, so either Street Fighter or maybe something more crazy being Marvel vs Capcom which allows for a lot more special bar craziness and mobility. V Triggers could be powering up or even transformation like Super Saiyan, supers are clearly for the special moves like Final Flash for Vegeta or Supernova for Frieza. Art style could actually be what they used on like what I feel is only one cutscene in the entire game of Xenoverse 2, where they show the death of Gohan in Trunks future, and it has like this serious shading and lighting and detail. It looks like it is from a different game and gives Dragon Ball some visual depth it hasn't had too much of. The rest of this game doesn't look this good lol Either this or something on the level of animation quality that is Guilty Gear Xrd, which uses 3D models to create an animated look.
(http://i.imgur.com/6dMZf85.jpg)