pilotsvrou,
Once you get a type rating you get a type specific MPA/IR, this doesn't keep your SPA ME/IR current, the MPA/IR does not give you any single pilot IR privileges (there is some cross credit when renewing/revalidating the SPA/IR, but I cant remember the exact rule). A current SPA ME/IR without the MEP gives you in the UK automatically a SPA/ SE IR. To do your first multi crew type rating a pre-requisite is to have a current SPA ME/IR. Under JAA, a second multi crew type did not require a current IR, I interpret under EASA this is still the case, sim training sessions for the second type rating would count as the ATO training for renewal of the MPA/IR, as such a second multi crew type rating does not require a current SPA ME IR? The alternate rule, aircraft one year, sim the next year is a reasonable new rule. Before about 2008 the ME IR could be continuously renewed or revalidated in the sim; as such plenty of people successfully completed type ratings with just the MEIR revalidated in the sim without issue.
As for raw data flying for a sim check; some one with a current ME IR at month 11 will struggle more than someone with a lapsed IR who has done a few hours practice in a relevant sim. So really no issue in only keeping the ME/IR current without the MEP. Also remember most jobs flying an MEP on a commercial basis will have far higher houra requirements than that needed to fly RHS on a multi crew type. So below 700 hours total time you probably cant get insured to fly an MEP on an AOC anyway.