Anyone been thinking about and/or working on something like this?

Combining SW Armada, X-Wing, and Imperial Assault.

Probably the map for Star Wars: Rebellion could be a good starting point, I think

Why stop there? Include Rebellion for a Galaxy Down view of things?

This would be amazingly difficult. Just think about the points cost and conversion alone, plus the fact that you're missing a scale. Where is our walker and tank sized ground battle infantry game?

Back in the 80's, a game company named FASA put out the Interceptor line. It was Star Wars in the barest of disguises. It had an Armada level, an X-Wing level, and a ground assault tank level to it, and it was integrated from the beginning. Everything was valued in credits, so there were no problems knowing how many grav-tanks were worth a heavy bomber, etc. Also it had rules right from the beginning about which values determined what when scaling, so you could have your starfighters strafing the battlefield while your tanks coordinated orbital fire from your capital ships in orbit.

Also, each level of play had rules for constructing your own ships, fighters, and tanks.

While admittedly the rules are far more clunky when compared to our current rulesets, and games took far longer, it was still a neat system to play. Time was the enemy though, and no fully integrated campaign lasted longer than a few battles. Heck, we played every other weekend through our whole senior year and only finished three battles, capital ship on down to the ground.