Oh, those are definitely two good ones. I would recommend just tearing down both, although I wouldn't object to putting a good, new dark ride in either one. But keeping them up is just a waste of good spaces.
Festhaus, 100%. It should be one of their prime locations -- that should be where some of their biggest and most spectacular shows play (it used to be, at least). Now the shows (at least, pre-COVID, when shows were a bigger staple) in there feel like afterthoughts. And the food is really disappointing. Panda Express just isn't something I want in a theme park, but that's just me. While I love the LaRosa's Pizza in other locations, I've noticed that the Festhaus' pizza is consistently lower quality than there.
Here's what I'd love for Festhaus: Clear out the arcade games and all that crap. Get a good bar in there, not just the beer cart. Install some more serving areas and make it a Taste of KI-type thing, where every eatery in the park has at least one selection -- maybe a BBQ pork sandwich, a burrito bowl, a burger, LaRosa's, Skyline, etc. Maybe have the Brewhouse staff operate the bar. I'm sure there are contracts and logistics that might complicate that, but it needs some variety. Or, just make it the park's high-end eating establishment (particularly if they aren't going to bring back International Restaurant).
And get a great show in there, not just some country filler or something with lame songs. I remember the days when Festhaus was home to an ice skating show, and it was packed. Do that. Or make the stage space smaller and book local acts from across the area to come. Or get a KI house band established. Right now, it just feels like a catch all.