The problem lies in scalability, and is apparent in Powerplay and the BGS.
Whatever actions can be taken at a high level have to scale from one player to potentially hundreds. A game like Civ would be horrible if 1000 players decided on what do do each turn for one country alone.
Powerplay was intended for the 'majority rule' like this and was unsatisfying because of that agency given to anonymous others (not to mention 5C), and that because the population is small (so majority rule becomes a liability).
The BGS works because each expansion / move can be done alone but does not affect other moves elsewhere- so all strategy is hyper local. Although it needs balancing there is huge amounts of strategy going on in the BGS, more than enough (which also dovetails well with ship activity) which then satisfies the 'higher' goal (of taking something).The other benefit to the BGS is that strategies are done via playstyles, so you really can play out things. All it really lacks is reward and a more visually apparent outcome on the ground / how you are treated.
I fully get what you want, but I don't think its possible in ED.
Honestly, I don't actually think it would be all that difficult at its most basic level. You need two things:
1: A meaningful set of rules that modify relative strength and weakness of defenses. Right now, it's basically 'friendly faction+distance', which is purely binary and doesn't leave any room for strategic thinking.
2: Meaningful rewards players will care about. People in EVE don't fight over meaningless systems, they fight over systems with real, meaningful value.
Take Civilization, for example; there are multipliers for defense based on terrain, you can build roads and fortresses and such to modify movement speed and defense, and the placement of your cities is also very important, to ensure you both exploit necessary resources while being suitably defended from attackers.
On a fundamental level, none of those things is particularly complicated. It all just breaks down to dice rolls in the end. But taken together, as a whole, it becomes far more than the sum of its parts! And any player could do any one of them, but it would only be taken
together that they would become truly meaningful.
Even better, this would have real, meaningful impacts on the way the bubble develops. Right now, powerplay is just this big fuzzy blob that makes no sense. If powers needed to develop in strategic and tactical ways, such that they maximize their ability to defend and attack, then suddenly the map becomes meaningful for once! Wars will actually develop along faction lines!
And the thing is, the game is already well-suited to this type of content, because it's basically a turn-based game
already. It already operates on week-long 'turns', so you can basically slot in lots of the existing aspects of similar games wholesale.