I would expect that to issue the IMC they will want a flight test if not done off the back of a SPA-IR. Which might be an idea to do anyway just the once to get your head around partial panel again. Then its just a case of paying your money to have it issued.
Personally I would keep it. You never know you might get the urge to do the FI course.
Things are up in the air just now with the new regs about to come in. My gut feel is that you would be at more of an advantage holding a ATPL with SEP and SPA-IR-SE than you would with a PPL and IMCR.