a) While it's good that you're willing to go with the flow, it really is, stroking your own ego about how awesome and unstoppable your dragon GMPC is and how he can just swoop in and do whatever isn't a particularly great move for a GM, because that's supposed to be the purview of the players. We want to find a way to bust into the fortress ourselves. Bee could cut the barrier, I've got fists that can work on magic stuff, Wyvern could shoot it down. Seeing anyone refer to their own character as "all-powerful" is fairly off-putting, at least it is for me, and why the crap would an "all-powerful" being need anyone to do anything for them. Trying to justify it by using fairly absurd game terminology you've been dragging for years does not make it better, we've established just how poorly thought out a lot of it is beyond the very basic idea of it being a crossover.

a.5) I'm not saying you can't have your "all-powerful" character, 'cause you're the GM. But I am extremely adamant in my belief that actually all-powerful characters should not be a thing, the idea inherently drains away all excitement and entertainment by virtue of having someone who is untouchable and undefeatable by definition, but you can have a super duper stronk dragon as an important NPC. The thing to remember with such characters, though, is that they're best employed as a plot device rather than an active character that goes out and does things. He needs to provide knowledge, powerups, quests, whatever that doesn't involve doing PC things, because if he can just swoop in and do everything for the players then there's no point in the players being there at all. From a narrative standpoint an invicible dragon showing up, being invincible and doing the impossible because he's invincible is a pretty shitty resource unless it swiftly leads to a severe fall.

b) If we move there I'm dropping the game. It does not look cleaner, in fact it looks far messier and has several threads and posts about the old game, something no new player wants around, because it leads to a general separation between the people who were there before and thus usually want preferential treatment and the new people trying to get into a game they're finding out has a long ass history some people aren't willing to let go of. This already happens with the returning characters and your own insistence that new ones should be weaker, as well as a general level of metagaming encouraged by the setting, such as it is, that lets old players better abuse what would usually be OOC knowledge to their advantage. I'm big on clean slates and new beginnings inspired by an old game instead of dragging its baggage around.