2 seconds of search of my profile would have proven to you that I have played AI war.
The behaviour that you're describing is exactly the one I want to avoid. The AI getting cheats to compete... doesn't appeal to me in most games. Ok, let's be honest. I think it's a artificial way of creating difficulty, rather than designing from the get-go a game whose mechanics make everything work.
From a mechanic point of view power, scaling is very, very difficult to balance properly (AI war being a prime example of that, it's saved by the numerous options it's getting and the fact that 10/10 ain't supposed to be won). When done, it has a high risk of giving the player a feeling of "it's always the same", and / or "whatever I do doesn't matter, as something unpredictable comes up to put me back at square one". SBR seems rather designed from the get-go with the idea of factions already in place, some being "early game" targets and others seem to be meant to be "end-game" targets. Adding another layer of scaling above that one sounds like much work for little benefit, with the constant risk of going overboard.
Also, lore-wise, it does not make sense from what I know of the game. Why would they have bonus stuff, and where does it come from ? Saucers just warping in to reinforced the survivors ? Why the hell did they not come in 5 turns sooner to save the AI I just killed ? If I kill the burlust first, the peltian get reinforcements but whatever reinforcement was meant for burlust does not come if the colony failed ? Why do they not retaliate seriously against people commiting genocide against them, if they have reserves ? In AI war, it makes sense - because the background of the game justifies it. In other games with "similar" mechanics (like most X-Com or jagged alliance clones, to cite only major ones), even the characters in the game lampshade that it does not make sense.
About the "problem" of moping, and the "51%" remaining, you're mentionning Civ which has multiple ways to avoid that particular issue:
- capturing cap is enough for military victory (self explainatory),
- science victory can be achieved (you've won wars = more technology + higher production, others can't reallly compete).
- diplomatic victory can be achieved (you've won wars = more money = buy votes).
That said, the "unit" AI in that game ain't really worth speaking about.
In SBR, there is a "subdue" mechanic in place already, which is clearly one of the ways to avoid moping (even if it's currently needing feedback). I suppose that plans for the diplomatic screen are going to show the other part. I don't see where scaling to the player is needed. Factions are already "supposed" to be scaled on the planet itself, and should gang up against you. If you beat them then ? You've effectively won the game ? Then you make it so the game recognizes it and gives you the victory you earned.