Just watched Black Narcissus for the for the first time in a long time and the climatic scene in that film gave me some ideas on how to rework Anakin/Mace/Palpatine's window scene which might work.

I imagined Anakin focusing all his resentment with the council on Mace and setting him up to confront Palpatine to see if he really would go through with deposing the Chancellor (and also to test Palpatine to see if the Sith really are as bad as the Jedi say they are).

Anakin snitches on Palpatine (which he knows he will do) and Mace goes in (not much change there besides framing the tone so Anakin is being more deliberate about it and less pondering, setting up how he would act as Vader in the OT).

But when he comes in Palpatine maintains the weak old man routine all the time (no unlimited POWER!).

Seeing the Jedi Master he dislikes the most with a blade at the Chancellor's throat makes him snap and he uses Force Lightning on Mace (he doesn't use it in the OT because he is a cyborg and any lightning he could generate would fry his life support system, as seen in ROTJ). Once on the road he falls for Palpatine's line on the Jedi entirely and by the end of the film he's so deep in the do-do he can't go back.

Instead of Sith eyes it might be more effective if he becomes more pale and cold so even on a volcanic world he looks like he is anemic and chilled (mirroring Luke's line in ESB about feeling cold and death near the Dark Side infused cave).