NO! never try to put a tube in a tyre, as soon as a tube tyre picks up a nail it will deflate very quickly, whereas a tubeless is sort of self sealing due to the thin layer of rubber coating the inside of the tyre, hence if you do pick up a nail (Most times anyway) it will result in a slow puncture.
If a tyre is over 70% worn I would replace it, and plug the other one, to keep as a winter tyre, where temps are lower, so is speed, on a newish tyre, i think the repair would worry me, esp if two up. I bought a rear wheel off e-bay, that now has a plugged tyre on it, to use as a spare shuld I get a puncture at home, simple case to change the wheels over, would rather do that than take the cage to sit in a Jam.