A couple of those would be tricky in the real world:
Mostly thinking of the 51% majority vote to remove one. In a vacuum it makes sense, but once political parties get involved and you end up in a situation where one has that simple majority, they can just eject all the opposing party. That sounds great, until you realize those who oppose everything you care about can do the same thing, and most of those other removal rules don't matter if the district they come from wants that. If they all involved managed to keep their nose clean, they can purge and keep purging. This could be mitigated though with ranked choice voting a multiple feasible parties to naturally prevent any one from getting that majority. Alternatively, make an additional rule that no one party can hold above a 40% representation, but that has its own issues.
The other one I see as potentially an issue is the third party enforcement thing, as that gets into a "who watches the watchers" situation, which is why the constitution ended up with the checks and balances implementation to begin with. If not properly done, the third party would basically become another house of government, and you would need a selection system and way to monitor it to prevent a similar tendency from coming up there, and then who enforces it on them?