I think Icewing -> Ghostwalker and Mountainshadow -> Dunkelzahn are the two best known 4th World -> 6th World connections. I believe Alamaise had practically the name name in the 4th World. I'm not aware of any other current major great dragons that were also mentioned in Earthdawn, although I'm sure there are some. I mean, all of them must have existed back then, but I don't know if they've ever been mentioned or if the connection has ever been made.
In my opinion, playing a servant of a great dragon, or even playing an immortal elf for that matter, is a bad idea. It puts you in a very different kind of game that takes away the freedom of shadowrunning.
That said, in our Earthdawn campaign, we did at some point end up working for Icewing, but we were desperate to get out of it. I think before that we were trying to get a powerful artifact to Mountainshadow, and we met him pretending to be his own servant, a drake called Darktooth. But I don't think it's something you should aspire to; it's something you should get suckered into and then trying to get out of it again.