Beyond the obvious difficulty of creating new footage for the Imperial Capital sequences the main problem is the lack of an immediate threat or boon to push the Rebels to make such a bold move, especially after getting such a kicking as seen in ESB.

Re-taking the Capital would be the capstone of the Alliance's struggle (Episode IX material).

The only thing that would motivate them to make such a move so soon would be something that could threaten them with total and instant disaster or some piece of intelligence which would make the plan seem a viable option.

Something like a Death Star, or maybe two or some sudden and soon to be fixed weakness in the Capital's defenses.

Without a danger of that...magnitude (ahem) or an opportunity of that scale what's the rush?

I'm not dismissing the idea out of hand but posing it as a question which might open the door to thinking about solutions.