As far as Im concerned this should be transparent to the end users, all they have to do is wait an extra day and coordinate the release. You don't release a patch to the public and gimp the online distribution models.
CoD4, Bioshock, and many others seem to be able to do this just fine over Steam...why not Relic/THQ?
The funniest part that I didn't know until a few minutes ago is that it downloads the patch ingame even if it's a Steam version. It's like they need to add some code to the game so that it knows it's 'special'.
Didn't THQ do that with Bioshock with this last patch? Make it so it knows its special so it doesn't have the SecuROM check? Bioshock didn't freak out when I started it up with Process Explorer running, which it did until the patch.