Ultra Instinct and Ego are just stronger forms for Goku and Vegeta rather than being techniques like in DBS
So here are my ideas for them to be added as special powers:

Ultra Instinct: Makes you dash all the time, letting you dodge more effectively, also grants a minor damage resistance while moving which increases with your speed stat
All angels should have this

Ultra Ego: Adds half the damage you take to your next melee attack, but gets replaced by the next damage you take, for example: Let's say one punch does 5 damage, and you take 50 damage then your next punch will deal 30 damage, but then you take 10 damage, then your next punch will deal 10 damage
All the Gods of Destruction should have this

Creo que lo que pides es demasiado complicado de recrear en un juego flash...
Yo igualmente no tengo ni la más remota idea sobre programación, pero me gustaría simplificar esta gran idea para tratar de incluirla al juego de una forma más facil.

Ultra Instinto: además de lo ya sugerido, si se tiene energía, esquivara los ataques de su enemigo pero se gastará rápidamente y aveces ni funcionará.

Ultra Ego: luego de perder cierta cantidad de vida, el personaje inflingira mucho más daño que antes.

You got to see that in terms of gameplay, not in terms of add this does that:
"Makes you dash all the time" = not funny to play

Ultra Ego already gain Ki when he takes damage.

And both transformations are already outclassed by DBS latest enemy. So there is really no need to make them OP in the game.

Oh I didn't notice that Ultra Ego gained Ki, but anyways I think that It could be nerfed with the speed stat to make it less annoying, It would let you dodge better but you couldn't be untouchable just by mashing buttons

although angels shouldn't get this then, they already move around like damn mosquitoes

maybe you get auto dash but it drains a fair amount of ki

Again, auto dash = unplayable = not fun to play