Markus Gisdol is interesting. Has spent the majority of his career taking over clubs battling relegation and turning them around, but hasn't had any long term success at a club.
His most recent job in Turkey, he only took charge for eight games and failed to win a match, but I was reading the reaction of fans and they mostly said he never stood a chance with their squad.
Has experience of some huge clubs (Hamburg, Kaiserslautern, Koln, Lokomotiv Moscow), is a free agent and has worked with Lutz before.
I'd like to think we're grooming Leven to be the manager eventually one day, but maybe be needs a term as assistant manager first. Bring in Gisdol for 18 months before it inevitably goes tits up, then Leven can finally get the top job.