In response to Nomadi's list, I think the Shiyooken (multi-arms) technique should be a trans because it WAS a trans in the show, and because 'power up' doesn't and shouldn't cut it as a transformation. The trans animation could be him getting all purple and sweaty like in DB, then regulating back to regular body with two extra arms. Also he doesn't learn KHH until later in DB so that could be his trans-exclusive attack, he did all the other moves pre-trans.
Have his 'Volleyball Fist' move as one of his special combos, or as a 2-hit basic melee
Dodonpa should be a yellow Deathbeam, with Rapid fire as a secondary, seeing as he already has genbeam, tribeam and KHH as beams.
He was the original Solar Flare (Taiyoken) user so I think the effects should last longer when he uses it.
Shinkikoho should be Tribeam as a beam/Tribeam as a blast like the genbeam/ball system, but with the afformentioned scope, the scope being him focusing all three eyes through the (hand) triangle to enhance his vision.
My additions into the list:
(assuming melee, ki blast, genbeam/ball and senzu are given)
1st form -- Normal
Dodonpa
Tribeam/blast
Solar Flare
2nd form -- Multiarms (Shiyooken)
Dodonpa
Tribeam/blast
Kamehameha
Solar Flare
One idea which isn't on the list is having 'Third Eye' as a move,
In the show: Tien focuses his third eye on Yamcha and copies the KHH when he uses it, instantly learning it
In ESF: If you're about to be hit by a move, you select the third eye like a regular move, its primary and secondary fires are block, but any move blocked in this way is 'learned' and can be used until you die and respawn, the move (e.g Masenko) then replaces 'Third Eye' on the list until death of Tien, when it changes back to Third Eye.