The reasons for EDFE not yet having IFR is not just political! The runway would need to be extended and that can only be done toward the west.... and gets quite close to the Autobahn (highway) and power lines. On the east end is a commercial area but more "threatening" are the very busy train tracks with passenger as well freight trains. For this reason there is a 250 m displaced threshold already in place (the reason for the 1400 m runway being only 1166 for landings on 27).
Then there's the question of missed approaches on RWY 27.... would have to go direkt into the Frankfurt control zone! So every time there's an IFR approach, all traffic on the EDDF 18 has to wait... not making airlines very happy. So the problem is actually trying to fit an IFR system for EDFE into the EDDF system!
All the possibilities are already being checked, but such a system cannot be installed on short notice... it has to be checked and double checked and go through all necessary authorities (BMVBS, BAF, DFS, plus various ministries, etc etc). That all takes TIME! It is being worked on, but whether it will ever get installed..... who knows.