As topic says; ive just moved back into wh spaceand was thinking how much better it would be to be able to refit from a can in station instead of needing to have it strewn about the place.
Put an alt into the new SOE ship. It’s perfect for short term or one player wormhole life.
Up till now I’ve been using a DST alt to hold the mobile depot and all the fittings/ammo/loot, keeping it safely logged out unless I needed it.
If you’re staying long term or don’t have/want an alt for the above, you can still put up a POS and a Hangar Array.
Wormhole Suitcase life is best life. 
But from which can would the fit take the modules?
I too like having refits in cans.
I make sure my main hangar is clean most of the time, with refits in cans, loot in a station hangar and other stuff in their own cans or sent to my alt that handles hauling.
This means my hangar has no items besides containers. It allows me to unpack the labeled can that contains the refits I want to use, and fit my ship with them.
It works well!
Refits in cans are a good idea and already possible.
I’m not sure if what you seem to want (that the game pull fits from modules in cans) is an improvememt though.
I’m afraid I’d never know for sure if the fits in my cans are complete if that were possible. Worse than the minor inconvenience of having to pack out the contents of a can to fit a ship is to realize that the can with the fit you brought along to a remote place is incomplete because the game grabbed one of the modules earlier to fit another ship. Don’t touch my cans please.