They will only get one crack at it, and if they fuck it up, all their money bullshit wont save them. There's a list out there on how to do it right, but you can be pretty simple: no cute or fuzzy things just as toys. Nod and smile if Lucas 'suggesting' things -- if he has moved on, then so be it. Think more grit, less gloss. The Falcon is legend --- uber-chrome sportscars aint. Be serious -- the original Darth didn't fuck around or take shit from anyone -- he was ready to kill someone just for disagreeing with him

The Force is mysterious; not a science experiment or trek episode. The entire EU fiction is horseshit --- completely ignore it
Using those guidelines alone should work.
Rebels is set between 3 and 4, so you have a 19-odd year time period to work in. Hell, I WANT to see different factions of rebels fighting, each other as well as the Empire, AND getting smashed to pieces. The Empire didn't stick around that long by being cute and diplomatic and listening to focus groups and senate commissions. It did it with sheer firepower and numbers, and the willingness to employ it.