The only thing you will need to keep current will be the MEIR. Both the MEIR and also the MEP ratings will need revalidated after 12 months. For the first IR renewal you can do it in the sim. The second renewal would need to be done in the aircraft. As for the MEP rating, you dont need it to start a Type rating course, only the MEIR has to be current.
As for keeping yourself marketable, keep flying!!! Some airlines will require you to have flown either 35 or 50 hours in the 12 months preceeding an interview. Some dont have any time limits, but generally you need to show you've been flying. Glider towing, para dropping etc etc....are all good sources of flying time. Not easy to get but it certainly looks better on paper that you've done something rather than sit and wait for a phone call. Also consider safety pilot work, put yourself out and about and you never know what doors may open.