On the other hand, carried water has the flexibility to be used as radiation shielding (reducing net weight), can help with thermal regulation (reducing energy requirements), as well as be used for life-support both as water and by carrying oxygen in a denser from which requires much less in the form of pressure tanks (again, reducing weight).
So the practical solutions can and will add your suggesttions into the mix and MAYBE offsetting somewhat the “extra-load-carrying” factors of stored water.
However, in doing so, a consideration will need to be how any use of water that you suggested will be diminished by the need for the same water for other uses. Suggesting it can for instance be part of shielding has to consider how the uses of the same water for other needs will diminish the shielding over time or need to be offset by other means as the water is consumed for those other needs. That opens the question as to other materials providing equal or better shiedling than water, but weighing less than water for the same amount of shielding.
No single aspect of “soltion” can be considered in isolation of all the varilable surrounding the use of something.
I still see these practicalities as what I think will find more research put into them than the research that found out how to slit the water atoms.
In part, I think someone will like the idea of doing the water-atom splitting for obtaining oxygen for long term space travel, and will imagine a very sophisticated “biosphere affair within the space ship” where water is always circulating, being used, being broken down, and being reconstituted in biolgioal mechanisms (bacteria) that rejoin free oxygen and hydrohen back into water. I think it might be sort of like a mini-biosphere-environment sealed within the external walls of the ship. It might even have “rain”. clouds and open resevoirs with artifical sunlight assisting in evaporation from which to capture water.