We have seen someone take Gundam figures and cross them with Star Wars Stormtrooper figures, successfully blending the two franchises, but someone else has taken it a step further. A custom Gundam creator named Justin has crossed the Dragon Ball universe into the Gundam world and it looks almost too good.
Justin has created tons of custom Gundam units, most of which take characters from other franchises and turn them into Gundam units. He has created a Thor Gundam, a TMNT Gundam, Wolverine Gundam, Toy Story Gundams, and more. They are all fairly detailed and pretty darn well done, but don't just take my word for it, check out his Dragon Ball x Gundam builds below (support his FB here).
Cell
Buu
Trunks
Vegeta
Frieza
[Kotaku]