Humans/other races can be allowed to travel to other planets VIA spaceships by capsule corperations for about 500,000 zeni. or something below that maybe?
They all should have split storylines for each race.
Humans could die in some specific planets that have a giant warning sign that if you die you will go to the other world. (which i will explain later in a few)
(The humans main goal is to go to get even greater training then what could be hosted on earth. so they go to other places)
Namekians Goal is to revive the old namek. so they search for a new type of dragon balls (not that GT bullcrap) on a different Namekian like planet.
(they eventually don't end up reviving ancient namek that was destroyed in the goku frieza fight so they end up making their own personal planet anyone can go to LIKE KING KAIS)
The Buu Race's Goal is to take on the storylines of the humans or namekians
Or end up reaking havoc across other planets.
Anyways back on the humans. When you die and go into the other world you meet King Kai which you could train even more and look even more taller or buff in a sense (like how gokus appearence gets slighty more taller and buffer as an adult in DBZ)
Eventually you find other quests to do in the other world and then you eventually go back to the real world because of one of the elder kais revive you so you could go back and forth from the other world to earth or other planets.
Namekians and Majin can possibly take on the other quests if they die in those specific planets that will send you into the other world.
