To be fair, W3W is already "spheroid-optimized", in that the named squares are quite close to 10'x10' both at the equator and poles. There are grid "skips" (see one here [1]) every so often to keep all of the squares close to the same size.
Also don't discount the benefit of their distribution of the words. If you're using voice input and trying to get somewhere, the system can guess which of multiple inputs you mean. If you're in Louisville Kentucky you're more likely to be trying to get to "captain.water.water" (a ~90 minute drive from downtown) than "captains.water.water" (located on an island in the North Atlantic). Do you have a mechanism (maybe a check digit?) to help with that?
[1] https://gis.stackexchange.com/a/195696
Also don't discount the benefit of their distribution of the words. If you're using voice input and trying to get somewhere, the system can guess which of multiple inputs you mean. If you're in Louisville Kentucky you're more likely to be trying to get to "captain.water.water" (a ~90 minute drive from downtown) than "captains.water.water" (located on an island in the North Atlantic). Do you have a mechanism (maybe a check digit?) to help with that?