From what I’ve read, in the first year one can revalidate the ME-IR in the sim, without actually revalidating the MEP.
You must hold the relevant class or type rating at the time of revalidation/renewal unless the IR revalidation/renewal is combined with the revalidation/renewal of the relevant class or type rating (FCL.625(c)(3)/FCL.625.A(a)(1)).
But FCL.740 states that when you let Class ratings expire, you have to complete additional training to renew.
No, it doesn't, it states that you must complete refresher training at an ATO
if deemed necessary by the ATO to reach the standard required to reach the level of proficiency to safely operate the relevant class or type of aircraft. Admittedly, few ATOs will pass up the chance to screw a few more shekels out of you for refresher training no matter how good you are.