Nope cross credit can only be applied for revalidation, both ratings must be valid.
So in effect you want IMC privileges on single engine aircraft. You haven't got a current rating IR/IMC so you will have to do a renewal check for anything. In that case go off and do an IMC renewal in an SE and apply for a Part-FCL licence and IR(r). Saves you the expense of the twin if you don't need it.
If you want an airline job, bite the bullet now and get the ME/IR back and keep hold of it on your Part-FCL licence.
For MPA/ME types you must hold a valid ME/IR regardless, SPA or MPA doesn't matter just a valid ME/IR
Last edited by nick14; 2nd Jul 2014 at 13:36.
Reason: Me/IR bit