have you already read rise/fall of the shiar empire
Rachel absorbs the powers of the phoenix sword (it has a piece of the force in itself) that was meant to behead her and after absorbing its power her golden phoenix signature turns blue and the shiar say the sword got weaker so rachel must be powerfuller now so with power change you think she would get??:;

1 her telepathy grows to empathy or precognition & her teke grows stronger, maybe on dark phoenix level and control over the white hot room to warp reality

2 Her chronoskimmig talent grows to chronokinesis the complete manipulation of time

3 her shadowform power grows and she can now steal the shadows of others possess them and absorb their nightmares and negative emotions and shadowteleport like betsy could and trap people in shadows

4 (this is the point i think it will grow to ) dark phoenix powers were backed by the power of the sun And jean when she had the force and was alive could create heat blasts and solar flaming energy aura’s SOOOOOOOOOOO i think she will get pyrokinesis not only for flames but also for bringing the judgement of the phoenix and burn away what doesn’t work.

I think it will definitely grow because as in X men the end she could open star gates something only phoenix hosts can do and she now still can’t
I also like professor X teaching her controlling her powers she thanks to him can outflank emma’s telepathy as bush leauge