My main issue with this is just the concern that introducing 'Michael' and Prospero at the same time lessen the impact 'Michael' could throw into the story since focus is split and Prospero's doing something distracted and evil-seeming, but if Solace doesn't care about that then it's fine. It [i]does[/i] make it a little weirder for them to start fighting since Prospero did what he did to try and get the Vongola group alone without harming 'civilians' but I can work around it.

Prospero could always assume his 'trick' just didn't work entirely, so there's not even any reason to assume 'Michael' is actually with the Mafia or anything identifying like that yet, as well.