I'd favor a proportional upgrade for any new attribute system : i.e a current 60att ship is 100% under the current system : so the new system will grant it enough atts to remain at 100% : a 45att ship is 75%, therefore it would receive enough new atts to be 75% under the new system.
I would not favor everyone being given a remodel for every ship they own : most would never be used by them and would end up on the market. Rather, I would prefer every ship to be granted an option (maybe a tick box on its ship page) to redistribute its atts, a one time only use : this would also cover inactives ships or seabed wrecks with no-one around to use a remodel on them. the subsequent owner would then have the option to upgrade it and redistribute its points.