Hi Martin,
hope youve already decided something for your MBA dream by now.
FYI, I am 31, I have a non-German background and have lived in Germany since 12 years, completed my dipl. ing. in Germany, and am now a system architect (yes, it has a lot to do with engineering and problem solving) at the biggest automotive supplier in the world originated from south germany. I only had roughly 3 and half year of works experience as I started in October to consider an MBA as a tool to accelerate and eventually change my career (I'd like to do more finance).
Meanwhile I got an unconditional offer from Aston and Strath respectively (I also got admitted from a reputable german university, not Mannheim, but I rejected it as soon as I had received the offer from Aston). And that despite lack of "managerial experience" like your perception to their requirement. Yes I did coordinate some of sub projects. But not the one with budget or disciplinary responsibilities.
I was kinda worry about that, but at the same time I started to work towards the completion of application (GMAT, TOEFL, references, essay preparation, find-mba forum, and so on :)). And look at what Ive got in my hands now...
So, if you are not yet considering to move towards the application, I can only say, just do it. Surely you have to put some extra hard works for your application in order to get admitted. But those b-schools are not very "tough" as they look like in their website (I am not talking about Harvard here..). They are not insurmountable. Ein Versuch ist immer wert....You'll never know....