Ludendorff might be a good candidate in the earlier weimar years, though without Hitler, the Republic is liable to be more rather than less stable. By the time of the Depression, he is, of course, rather discredited, as are various other would-be generalissmos (Kapp comes to mind). Still, if he manages to get backing from buisiness interests in a 'Red scare' scenario, a Ludendorff-Hindenburg ticket is just barely imaginable. IIRC they hated each other, but then, Hindenburg despised Hitler and worked with him.
Another alternative would be Goering. We tend to see him as a somewhat ludicrous hanger-on on Hitler's coat tails, but in the late 20s and early 30s, Goering was an active and dangerous powerbroker and quite a few people were not at all sure which of the two called the shots in the Nazi party. If Goering places himself at the head of a Nationalist, fascist-style movement, he stands a good chance of winning the support of the plutocrats. He certainly was happier in that kind of company (Hitler was notoriously uneasy around 'aristocracy', Goering revelled in luxury).
Of course it is just about possible that Germany doesn't go the fascist route. I doubt Weimar has a chance at staying a stable democracy past 1929, but something like 'directed democracy' under a CEO-chancellor and technocrat ministers is a distinct possibility. ESpecially as a lot of the 'muscle' siphoned away from the traditional right by the Nazis will now be available to Stahlhelm and (to a much lesser degree, unfortunately) Reichsbanner. Their parties were traditional conservatives happy enough to work in a the context of a multiparty system and bourgeois voting stuctures. Many of them secretly harbored monarchist sentiment, but I don't think anyone seriously considered reinstalling Wilhelm II (not to mention the French would never have tolerated it). Thus, something like what they planned when they 'hired' Hitler could actually work ATL, with a figurehead President and a ministerial technocracy. Shades of Franco.