Rudy said he had NO intention of re-signing with the Kings before his injury. I don't like that. It speaks to his loyalty and commitment. In his defense I don't know how much of this was related to being a teammate of Boogie. If degree of that sentiment was not wanting to play with him, or being around the extracurricular drama, I think he was justified in wanting to move on.
From a pure basketball point, I don't think he can help the team. His defense was bad before he busted his Achilles. Its not going to get better when he returns. His lateral mobility is not going to get better. In regards to having him opt-in being a positive so we meet the floor, I completely disagree. Its better to have flexibility to chase guys you want and work favorable deals (absorbing contract for 2nd rounders) when opportunity strikes.
Even if you don't spend to the cap floor, the additional dollars get spread between players on the team, which increases goodwill.