I'm writing a research paper on the Wiemar Republic right now. I would comment, but I have Wiemar coming out my ears right now and I'm trying to relax. 
One thing is for sure, change things slightly and you'll have one hell of a ripple effect; without major effort. Hitler's rise to power was a fluke, no matter how well planned it was still a case of right place/right time. We could have ended with a up a dictatorship under Papen or total civil war...perhaps a communist govt., the list goes on.... I would love to see a clever TL about this area. Keep at it Xahar. I'll comment when my mind is less scrambled.
I agree. The late 1920s/early 1930s was a period where pretty much anything could have happened. Hitler becoming Chancellor was a fluke, even if it had huge consequences - but it bears mentioning that, as early as January 1933, Hindenburg said that he would never dream of appointing "that Austrian corporal" as Chancellor.
Either way, very interesting thread, I think a scenario where Marx instead of Hindenburg becomes President could prevent Hitler from becoming Chancellor - but then, how would Hitler have fared against Marx in the 1932 Presidential election? And, if the Nazis couldn't seize power through electoral means, would Roehm and the SA have tried to do so in other ways? Would the Communists seize power instead? Would we see a civil war? There are loads of possibilities. Keep it up, Xahar.
