There's a reason it doesn't happen a lot.
If they thought he was worth it, the should have done long term deal this year or last to give some cap relief. If you can't come to terms, let him walk. Now we're going to spend close to half our existing cap space on one guy who's not worth it. If he plays poorly it will be a waste of money. If he plays well, we won't be able to afford him next year.
We are rebuilding. You want guys signed who will be here for the next 3 years. If Tru doesn't want to be here - say goodbye and move on.
Are there overpaid free-agents? Yes. But what does that have to do with the franchise tag being used in back to back years?