I think Indy should keep Granger. If he's healthy and buys into the team, they're a top-tier contender with a very real shot at knocking off Miami. Added to that, he's an expiring contract that comes off the books at the end of the year, freeing up money that will then be thrown at Paul George (who will likely command a max contract, or close to it). Hard to imagine a deal that preserves their status as contenders without adding a lot of long-term salary to their books. Not sure a team like Indiana is willing to sink that deep into the luxury tax.
From our side, I agree with Lightspeed - if he's healthy, he's in that tier of not-quite-stars who might put you in the playoffs but won't make you a contender if he's the lead guy. Bad place for a rebuilding team to be.