Expired MEP and SP IR renewal
 

Based on an individual MEP renewal program, can an expired MEP be renewed in conjunction with a SP IR? They have both been expired for over 3 years, but I have been flying commercially in multicrew IFR ops full-time.

You'll need someone else to confirm this, but I think that with a current MP IR, you should be able to get a SP IR pretty easily, and I don't see why you couldn't combine that with your MEP training/PC. The thing to do though is talk to your friendly ATO representative and the examiner in question so that they can figure out the details for you. It's their signatures you'll need, so someone on the internet saying that it should be possible is not enough ;)

You can combine the renewal of an MEP class rating with the renewal of an IR-SPA-ME. The proficiency check must be done in the aircraft. You'll need training as required (likely to be a mixture of sim and aircraft) then to take the check.

Assuming we're talking UK or EASA...
If you have a current multi-pilot IR issued by the same Authority (eg both UK or both EASA) then to renew or revalidate your single pilot ME IR you only need to complete Section 6 of the test schedule on instruments - EFATO, asymmetric approach to go around, asymmetric circuit to land. There is no problem with doing the ME class rating on the same flight. The reference for cross-crediting is Appendix 8 to Part-FCL.