I am a big fan of the grand crossover, but I can see some issues. Like you said there is a bit of a glut in the D&D in space genera at present. Personally I like to scavenge bits from games. I'm much more concerned about the actual compatibility issues. St&SP is a very different system from LL or MF, trying to shoehorn the game into the LL family would be difficult with out loosing much of it's charm. On the other hand coming out with a revised version of the original system so soon after its release might not be received well ( I know I would be less likely to buy it.)
The obvious solution of course is Starships & Spacemen GORE edition.