Residential door key control solution?

I would recomend an ICLO/LORI Deadbolt. You might have to do some enlarging on the bolt-hole and on the door frame. It uses a mortise cylinder so you can order the cylinders from the factory or have a locksmith pin them for you.
Arrow makes some decent residential deadbolts that can use Key-in-Knob cylinders.You could order your KNK cylinders-then swap them with the Arrow
You could go with a Locksmith only keyway also. That way you would'nt be screwed because another locksmith would have them or could get them for you.

do ya have a response or not ?

Medeco Biaxial comes to mind.

If the shop goes out of business, it is likely that the records, blanks, goodwill etc would be sold to another shop.
If you do have the misfortune of being left high and dry, buying a new lock would not be the end of the world. If you cannot get any more keys made, it is probably time for a lock change anyway. If you charge a reasonably stiff fee for extra or lost keys (this has been discussed here previously) this would yield more than enough money for reasonably regular lock changes.
In reality another locksmith could most probably just supply new plugs (the part that turns) or cylinders when a re-key is needed.
Unless you are using Medeco (and some other brands), it would pay to have a diferent keyway used, so any old keys retained by residents cannot be turned into bump keys for the changed cylinder.

Dang Key, You are one hell of a lurker-Waiting in the shadows you are!! Just kidding. Actually I slipped-My bad
goma.

figured as much :-)
happy holidays to you & yours