I say keep what you enjoy! Personally I can't have enough shrimp tanks, but I was a hobby breeder for many years, opened an LFS, and kind of burned out on carrying buckets and hatching brine and so forth so shrimp are a welcome low-maintenance change of pace. But a betta really doesn't require much. I certainly don't think one would find your Dutch style scape boring! Mine have never been big hiders anyway. If you've had bad luck with them, I'd try a new source because once acclimated they should be near bulletproof.
I keep a betta in a shrimp tank, but it's a 50 gallon, he's the only fish except for an L cat and he's outnumbered around 200 to 1. But I'm sure he eats fry daily, just in a tank that size can't begin to keep up. In regards to your cycle, fish would be much safer to put in than shrimp generally speaking. So the safe wait time would be much shorter for a betta if that influences your decision.
Nothing good happens fast in an ecosystem.