Franchising him is the right move. You spent the first overall pick on the guy, at the very least you try to get something for him rather than letting him walk. And the very worst, you pay him a big chunk of money for one more year with no long term commitment.
If he wants big money, the right move is to franchise him because he hasn't shown he deserves a long term commitment, but you guys are right, his replacement also isn't easy to find.
I agree, use the non-exclusive franchise tag on the guy for now. Let him have another year to show he can fit in the new offense, or look for a trade partner willing to give up a couple of high picks we can use to replace him. If we could get a 1st and a 2nd for Long, I'd make that trade in a heartbeat.