I just want to point out that putting minmaxed fleets in the game to fight would decrease number of viable builds, not increase it. The harder the game the better your build/fleet needs to be so the less room is there for personal preference and variety. Imagine a hypothetical scenario where the community arrives at what is mathematically the perfect fleet composition and it's then put in the game - then to beat it you must use the exact same composition(since we know it's the best) AND pilot a flagship yourself to break the stalemate between the two.
The main reason why Ordo is the benchmark isn't because Remnants are the toughest enemies(though they are) - it's because they're the only enemies worth "farming". If you want Alpha cores, you need to fight the Remnant. If you want bucketloads of XP, you need to fight the Remnant. If you want to get Omega weapons... well you fight Omega but they have same ship profile as the Remnant(high tech, shield based) so it's largely the same thing.
Non-Remnant endgame fights already exist in the game. You have Hegemony inspection fleets, you have Derelict bounties, you have elite Mercenary fleets, etc. In fact, many fleet compositions effective against the Ordo would fail in these fights(good luck using Wolfpack Tactics against a station for example, and I have doubts about how well Gryphons would do against Tri-Tachyon carrier spam) The difference is, there is never REALLY a reason to fight them in the first place because they don't offer anything unique compared to the Ordo. It's all just money and you can get money from elsewhere.
So my idea would be, just give the player incentive to actually bother with something else than the Ordo. Derelict bounties could spawn with a mothership and drop a colony item for example. Elite mercenary fleets could actually reward you a ship with S-mods(to my knowledge that's currently impossible, all the S-mods will be conspiciously missing from salvaged enemy ships) As for stations, these are largely missing from the game at the moment - there are Pather and Pirate station fights that are mandatory but they're almost universally low tech and never go beyond Battlestation in size. Maybe some new type of bounty on a Tri-Tachyon rogue research facility where you can actually try your luck against high tech Star Fortress?