Keep Dragon Ball the same, and the Saiyajin arc mostly the same.
Don't say Freeza is the strongest in the universe, say the Galaxy.
Have Goku die and pass the mantle on to Gohan, and have ChiChi pregnant (pre-space trip sex) with Goten.
Add more stuff to the 3 year time gap, and keep Mirai Trunks there, just have Bulma get killed off in the future.
Mirai Trunks arc plays out as normal, no Mecha Freeza though, so no breathing in space so I can blow up the planet bullshit.
Have Gohan and Trunks bond, so that when Trunks dies, it's the trigger for Gohan, rather than 16.
Make Bojack canon.
Have Mirai Trunks go to his future and return at the start of Buu.
Make a 100 episode arc about Teen Gohan exploring the world and make it basically Ranma 1/2 levels of romcom with an opening as good as the first OVA OP for Ranma.
Keep Buu the same, with Goku coming back and all, but we get Gohan and Trunks bonding kino.
Final arc is Great Saiyaman Trio versus The World.
Then do a separate anime for DBO