If you were editing each movie individually, I would agree that ‘saving the reveal’ would cut too much out of ROTS to be worth it. However, if this is a 3-in-1 idea, then there would be plenty of material even if it leaves out Anakin’s fall to darkness.

Of course with so much of Anakin’s part cut, it makes a good argument for centering the story on Obi-wan instead.
Start with his relationship with Qui-gon, the emergence of the Sith, and him taking Anakin as his apprentice.
‘Your apprentice, Skywalker, will be.’
Hard cut to Zam’s speeder weaving in and out of traffic, Anakin hanging onto the roof for dear life. There can be the occasional scene between Anakin and Padme to establish the plot, but most of the scenes with Obi-wan discovering the clones would stay and be the through-line for this section. Continue an abbreviated film with ‘Begun the clone wars have’ and go from the ships lifting off into the Coruscant sky to Anakin and Obi-wan zipping among them in ROTS.
ROTS would focus on Obi-wan and his growing unease at the state of the war. Anakin is painted as more heroic here, with little of Palps insinuations. Focus on Anakin’s love for Padme and future children. End Anakin’s part with him waiting in the council chambers. Order 66 is the big emotional culmination of the film. The implication is that Anakin died defending the young Jedi, but his children will carry on and avenge him. End as ROTS ends, with Obi-wan delivering Luke to Owen and Beru.