Question to German's about Felix Sturm

No, it wouldn't.

1. There is no PPV infastructure in Germany. There is only one Pay-TV Channel and it's been struggling for 20 years. The business model was never accepted. I doubt any German would be willing to pay 30+ € for a single TV event. (I find it unbelievable that so many Americans are...)
If a fight would air on Sky, due to the limited number of subscribers, they'd be lucky to get 500.000 viewers. If they made it PPV it would not get 5% of that, because

2. Germans don't know Floyd Mayweather Jr. The only fights of his that were broadcast here were the snoozefests against DLH and Hatton. They aired at 5 a.m. with abysmal ratings. So it wouldn't be a superfight. Floyd would be regarded as a tiny guy who comes to challenge "Super Felix", who has been uptalked for years by the worst sports-commentator in the business.

There is a reason that the Klitschko's do what they do on free tv. They are true superstars and if anyone -in any sport- could get away with it, they might be it, but they wouldn't even dare to try.

As to the OP: No, Sturm has no mainstream appeal. He got sweet ratings for his fights. But that's most likely due to lack of alternatives, because while Boxing is certainly a very popular sport in Germany (to watch only though, not to practise) the only fights that are aired are those by the handful of mediocre "German" (read: Eastern European) boxers like Sturm, Abraham, Huck, Sylvester, Ghevor, Dimitrenko, Krasniqi, ...