Alright. I like the sound of making an AU using elements from both their verses into one new setting. We can still get that same learning curve from jamjars I think, if we scale-up the setting perhaps. Instead of country-level politics we can make it into a planetary scale, with Britannia as a space-faring empire that could have taken over Earth and the major human colonies, while Troy's from a separatist faction from farther colonies who remains loyal to the old Earth government without the imperialism. So that's one way we can handwave why their technology is different from each other.

I like the Knightmare Frames; and we can say the Archon supersoldiers from his world with their power armor suits and genetic enhancement are the counterpart to that. We can have some assumed CR that they often meet in the battlefield and have grown a mutual respect for each other as rivals, but they never really get the chance to sit down and talk as people to get to know each other on a personal level. So now they have a chance to do that. We can start our PSL after the war between Britannia and the outer colonies, with Troy now being chosen as a new king of the outer colonies. And maybe they can join forces against a new enemy, whether it be fellow humans or aliens.