I think, the team should do it like this:
Buu -> Evil Buu -> Evil Buu (with Gotenks and Gohan) - > Kid Buu
Goku -> SSJ Goku -> SSJ2 Goku -> SSJ3 Goku
Gohan -> SSJ Gohan -> SSJ2 Gohan -> SSJ2 Gohan (adult)
Freeza -> Freeza (form 2) -> Freeza (form 3) -> Freeza form4 - perfect
Cell -> Cell (form1 - android ; male) -> Perfect Cell (form2 - androids ; male and female) -> Cell (form1 - android ; male only***)
Trunks -> Trunks SSJ -> Trunks USSJ -> (any ideas ? - perhaps Powered up Trunks SSJ)
Vegeta -> SSJ Vegeta -> SSJ2 Vegeta -> Majin SSJ2 Vegeta
Picollo (add turban and cape) -> Picollo (without turban and cape) -> Powered up Picollo (namek fused) -> Picollo (Kami fusion)
Krillin -> Powered up Krillin -> Mystic Krillin (form1 - without hair) -> Mystic Krillin (form2 - with hair)
I want Copyright for this