Specs. . .
How the game is visualized in ones head in terms of both position, value resolution, and short and long term strategic considerations has TONS to do with the time put in to battling, and for me at least, that is tied directly in to how specifications are laid out and especially in to the value ranges being considered. It's much easier to throw 1-10 or 1-20 around in your head than 50-7440 etc.
Battle. . .
I like the concept of the Order of Battle. The reason is because it makes engaging in a battle more of a known commitment in terms of what you will need to do and put in to it and how a conclusion is reached. It also helps hasten many things with respects to Retreats, surviving fleet constituents etc. Also I like that it puts things in a neatly framed perspective. All the choosing to be done is further constricted to given Phases, it will eliminate a lot of loophole gaming by more definitively spelling out what can be done when and where.
Unit Roles. . .
I really dislike idea of going back to One Ship + Support. It worked before because of our numbers, you could put together a whole fleet with several people. The only way in my mind it makes sense and woudl work out capturing the "feel" of the game, is if it were a restricted scope*, meaning not a whole galaxy at large. This is not something I am at all opposed to.
For Fighters/Aux/Support, rather than treat them as a finite individual unit attached to a larger unit, we could just treat them as abilities of a sort of that greater unit. So it's not so much fighters get tracked and deployed and attack individually or are destroyed, but they have functions that factor in to a Capital Ships greater abilities. Then the amount of squadrons a ship would have could translate in to how many times in a battle a certain ability could be used, or to what effect? This also eliminates mass delpoyment of every support unit a ship has for every battle creating swollen globs, and forces "Support" to take on the respective roles they are meant to instead of generally augmenting any kind of attack.
Scope. . .
Big & Simple is doable in my mind, but like I say I think it's tied in to more how you present Units and what they can do. The OoB will help straighten things out immensely and 'nsync to it's name, help establish some Order. You can have a person with a fleet of 5 ISDs, but then everything those ISDs can be used for needs to be tightened up and VERY SUMMARILY presented, their support would need to be tied more directly to them, and tracked along with them as well as a part of their actions more or less, rather than separately. Basically Aux would have no durability associated with them, they'd be able to be Countered/An Ability Rendered Uselses by other Support Abilities of opposing players uses.
Galaxy scope wise, you could take a single planet and a single battle and make that the focus of the game. There's really no more pivotal event in the Galactic Civil War era/The Star Wars we most all know and adore most intimately/EmpireVSRebellion than the Battle of Coruscant/NR Invasion. Something of such magnitude could go on for years IC and involve any entity conceivable. It'd take careful design (what doesn't) but you could set it up to be a really long drawn out chess match for the Battle itself. Possibly too unorthodox to draw interest, but a cool concept to me.