Gimbal Cabin?

The most famous gimbal project was this one, SS Bessemer

Why swinging saloons failed | How It Works Magazine https://www.howitworksdaily.com/why-swinging-saloons-failed/

SS Bessemer - Wikipedia https://en.wikipedia.org/wiki/SS_Bessemer

 

That only takes care of the motion on 3 axes (rotation). It will not make any difference on the other three: translation.

 

Sometime ago Skyak proposed a sorta similar but much less ambitious idea in a thread I started about handicapped facilities on "affordable" boats: Small Cruisers for Handicapped Access and Care https://www.boatdesign.net/threads/small-cruisers-for-handicapped-access-and-care.52868/#post-730180

His idea was essentially to suspend seating from the ceiling as a sort of hammock chair. Since the thread was mainly about bathroom facilities I thought he might also be indicating your standard composting toilet.

Now, I'm also a fan of the stabalized monohull concept which because the amas have limited displacement compared to the total does have a damping feature in terms of the speed of rolling (where a trimaran is stiff and quick) so while we're talking of mechanical madness what about a sprung parallel link suspensions for a trimaran's larger amas rather than a stabilized monohull?

That should result in, for those in the main hull, still small but not necessarily as quick motions.

Goes without saying that a failure in your springs / shock absorbers / air shocks could be bad.

Edit: I know suspension systems have been used with fast catamarans, to reduce the sense of pounding, but this system would be for moderate speed craft. Though I suppose a fully sprung catamaran of moderate speed properly designed might feel like it rolled less (the up and down would obviously still apply, though possibly in many cases damped considerably).

2nd Edit: a quadmaran or hexmaran (two rows of inline amas) might do better with waves from angles.