This is pretty damn close to what Weimar elections used already - although Weimar didn't fix the number of seats but made that dependent on raw votes cast.
Yes, but I'm also adding a threshold. It's not much, but the results should end up looking more like 2001 (especially with the DHP).
There was (sort of) a threshold under Weimar, too. As I read you, your threshold kicks in only at the federal level, so regional parties like the DHP should be fine(-ish). This is very like Weimar, where regional parties found it easier to get in because federal seats were proportional... with the big caveat that they could at best double the number of regional seats won.
