I think for "V" to mean staff transpo, it has to come before the basic mission designator - for example, Air Force One is a VC-25, whereas an AV-8B is not a VIP Harrier. 
 
Sputnik, what's funny about that navy thing is they, like the Air Force, operate the HH-60 in a rescue role - however the USAF HH-60 is based off of the Army UH-60 platform, and the USN HH-60 comes from the SH-60 Seahawk platform.  Yes I know they're pretty much the same thing, but there are some differences - I don't think the SH-60 has windows for door gunners behind the cockpit, and they've got that large two-wheeled underfuselage tail wheel instead of it being way in back. 
 
I think politicians or staffers decided that the "M" for "MV-22" means "Marines"...