It would be epic to have gravship-friendly hygiene options which are perhaps more resource intensive while using less precious floorspace.

Water tanks: Similar design to gravship fueltanks. Fillable from bodies of freshwater on the planet's surface, via a hose or pipes and a shipside pump. Higher risk of contamination if surface water isn't filtered?

Water recycling: wastewater is filtered, purified, and recycled to refill the gravship's water tanks. Some lost in the process perhaps, eventually necessitating a planteside refill.

I think the rest of the existing Bad Hygiene features are already pretty compatible with ships, where appropriate :D