Thinking about it, if I was managing Grant I'd put him on the older Rahman/Briggs career path. Fight half a dozen cans to get the name out there, then try and land a fight against Vittles.
He's switched over to training with Jeff Mayweather and is pencilled in to fight Carlos Takam in March, I believe. The Wilder fight has been suggested but I don't think more than that yet. He didn't fight at all in 2012 due to two things. Firstly that the Botha fight was meant to have a rematch, but that fell through after wasting a few months. After that, a couple other potential fights didn't happen when Grant was unhappy at the lack of prep time offered. Turn up with your boots a couple weeks before kind of thing. Which I guess would include the Fury offer, don't know for 100% certain. Sandman, I would definitely agree with your approach instead when it comes to older fighters with a bit of name value. Get busy, even if it's just cans...gives you profile, gives you a win streak, keeps you sharp. Waiting for the big one can happen occasionally (such as with Rahman recently) but it's rare, even in today's depleted division.
He should have a couple tune up fights then fight Wilder, he can still hit and he'd be a genuine test for Wilder.