I’m keen to see this idea! Your ideal script looks achievable given the original scene.
From The Phantom Menace, at 19:00 Sidious says ‘naïve’, which could substitute for ‘weak’ in your ideal script. Also, in Attack of the Clones Sidious calls Dooku by ‘Lord Tyrannus’ at 2:12:35, which may be useful if it matches the tone of the spliced dialogue better, though it may be a little confusing to call Dooku by his lesser used title. There’s music in both scenes, but it doesn’t sound too prominent.
Maybe the line in TPM at 40:00 - ‘you will then have no difficulty in taking the Queen’ - could be useful for Sidious commanding Grievous to capture the chancellor? But you’d have to add sfx to match him speaking through the hologram. He also says ‘chancellor’ in a sinister manner at 1:32:10 in TPM, which could be spliced with the above line.
There’s probably dialogue useful for Grievous somewhere in the Clone Wars show, but I’m less familiar with that. Even thought the actor is the same, the sfx there sounds a little different to me than in the films. I’m not sure how well they’d hold up side by side in this scene.
Thanks, that’s helfpul!