Binding MMORPGs together

In a recent interview in Wired, Blizzard COO Paul Sams stated that their next MMO would be "significantly different" from WoW, so as to not canibalize WoW's user base. Now I have this great idea what they could do: Blizzard could do a fantasy space-flight MMO with a twist, with every planet representing a World of Warcraft server. So there would be a huge intergalactic war going on in space in the new MMO, but the outcome of PvP events on various WoW servers would have an influence on that war. The two MMOs would be bound together, each having an influence on the other, and players could communicate from one game to the other.

Of course the idea isn't actually mine. And it isn't actually Blizzard's either. In fact the idea is from the makers of EVE Online, who want to create a MMOFPS called Dust 514. Every planet in the EVE Online universe would be a battlefield in Dust 514, and the PvP in the two games would influence each other. Still early days, and a bit hazy about how exactly all of this would be working. But the idea to bind together two MMOs is out there.

Is this a good idea? I'm not quite convinced yet, because there are huge, obvious pitfalls. In spite of what EVE Online marketing videos try to tell you, already the influence of a single player on the galaxy of EVE is rather small. So who wants to play the Dust 514 grunt working for that insignificant EVE player? Or what EVE player wants to be told that his guild just lost a planet because the Dust 514 players on their side went afk? You really can't make the events in one game have too much of an influence in another game, as people get frustrated to be thwarted by actions which are not only outside their control, but even outside their game. But if there is relatively little connection between the games, then why bother?

I want you to help with a thought experiment: Imagine whatever MMO you are currently playing. How would you make a second MMO from the same company bind to your game? Where would the two games be connected, what would be the influence of your game on the other game and vice versa? Do you think this could possibly work?