The day has come. After 400 hours and over 2 hours managing part upgrades, i've done it, got Asuka on P3 (2 copies from banner, one from roulete pledge) and rainbow eva 2 (two copies + 3 spare parts, 5 upgrade kits).
(those arms have very low hp huh)
I reached full pity of 90 + 120 but got VERY lucky to win the 60/40 on second one or else i would be kinda mad. If you're going to roll 2 copies be prepared for the worst. She has no good mech mods cause i aint got shit and they didnt put ranger in expedition, i was going to scrap it for 2 handed weapon mods (rip).
I haven't even tested yet, but i'll post some thoughts later. I have to finish the story chapter and also genshins main quest.
PSA: They will be adding a new "core upgrade kit" on arena shop and rare events. Those kits work like the common kits you get on roulete but unlike them, they can be upgraded by those kits into a gold 2 kit, then upgraded further to a gold 3 kit that can be used in gold 3 parts.
This means the game adds a method of rainbow mechs with only 1 copy now. Instead of 2 copies + 8 upgrade kits, now you can use 1 copy + 8 common kits + 4 core kits. Plus the other blue and purple foods ofc.
This should take a long time, probably +6 months but it's possible. I am planning on getting one copy of eva-0 and rainbowing it, even if it's not a particularly strong mech. I have no good heavy mechs and that one is good for any multihitter.