My concern is convincing airlines to do this. They always go for as many seats as possible. Also, beyond the US, UK, Canada, and other ‘first world’ countries, what other countries are going to mandate this?

I hope this gets lots of attention! I do believe that there can be even more airlines can do, after all they can make car seats that both meet safety requirements and are able to be stowed away in the floor so you can use the space to haul stuff. Why can’t they do the same in planes and have it setup for wheelchairs when stowed (i.e. mounts for wheelchair straps to secure it in place)? In any case, I hope we see more inspired engineers like we see here!