How would we sign him?
Haven't put down the numbers, but I assume we could work out a sign-and-trade deal with Brooklyn.
If Harden decides to leave, I bet the Nets would rather trade him to his preferred destination than lose him for nothing.
For instance:
Smart + Horford + either Timelord or JRich + pick(s) for Harden
I'm too lazy to check the numbers, but I believe it's possible to end up below the apron after the trade. Again, this is assuming Harden wants to leave and the Nets face the dilemma of letting him walk vs facilitating a sign-and-trade deal for him.
For the record, I don't think Harden would be an ideal fit alongside the Jays, cause he'd take the ball away from Tatum in the half court. That said, you do that trade in a nanosecond if you are the Celtics. A big 3 of Harden, Tatum and Brown would instantly transform us into legit contenders. Imo, we'd become the best team in the East (if not in the NBA).