By design, m-cMerge can be used for general m-c push marking, not just merges. This makes it useful for marking a bug with a large number of discrete patches (ie bug XXX - part 1...bug XXX - part 10). glandium asked if m-cMerge can do the same for m-i.
Possibly slight feature creep, but I think this could be a hidden feature, as with the ability to accept 'tip' and hg rev/pushlog urls. It could accept inbound rev and pushlog urls, and do the right thing on noticing /integration/mozilla-inbound' in the URL. 'Resolve' should be automatically disabled in this case, along with auto-whiteboard morphing. I'm dubious about target milestone setting too: I'm just old-school "until it sticks to m-c we can't say what milestone it'll ship in".