I sometimes hear ~~まんねん used to mean ~~んです in Osaka/Kansai. I think they use...
- ちゃいますねん/ちゃいまんねん to mean 違うんです (the polite forms)
(We use ちゃうんです to mean 違うんです in Kyoto.)
- ちゃうねん to mean 違うんだ (the casual forms)
- ちゃいます to mean 違います (the polite forms)
So I'd say...
- 疲れまんねん means 疲れるんです (the polite forms)
- 疲れんねん means 疲れるんだ (the casual forms)
How commonly is ~まんねん used?
I think we often hear older men in Osaka use ~~まんねん. We don't expect young people like high school/college students or stylish businessmen in smart suits & ties to say 疲れまんねん (unless they're joking) even if they're from Osaka.
...are the Seagal ads trying to portray a certain image by using this pattern?
Likewise, we expect an action star like Steven Seagal to always look cool and perfect. We don't expect him to look exhausted and whine 疲れまんねん, right after he dispatches his opponents or in the middle of a car chase. (The こう in こう見えても refers to something like "He's doing all these things with no difficulty.") And, he abruptly confesses; "こう見えても、疲れまんねん" in a tone that an older male Osakan in shabby clothes would use. This is quite unexpected, so that's why the commercials are pretty funny to us, draw attention and remain in our memories (and actually that's what they'd want their TV commercials to be, no? ^^) P.S. Sorry for my poor English.. please feel free to edit, TIA ^^