Like Davis a lot - had him 106 overall and in the 3rd/4th range. Super quick with his feet and eyes in coverage, and I think you nailed his primary hurdle - adding some size and stength. When you factor in his ball skills and the importance of the position, it's hard to understand how he wasn't drafted. Some guys just slip through the cracks. Justin Reid fell to the 3rd. Quenton Meeks went undrafted.
Anyway, I think he's a great pick for most improved. As a Senior he posted 15 PBU's, 5 INT's (3 of which he returned for TD's), and 4 sacks.
Also like the OP and some other posters' Gesicki pick. I'm not going to pretend to know how long it will take, but I think he'll be good. It'd be big if Miami could add Foster Moreau to give then an inline TE who also has some juice. Drew Sample is a solid tertiary option.
If the option presents itself, the best deal is a TE coming off his rookie contract like Ebron. Because he was labeled a bust, the Colts got him on a 2-year deal at 8-per iirc. I wasn't the biggest fan of Ebron coming out. Thought his physical talent was a little overrated, and he looked like a player who would need time to develop at a position that takes almost everyone a while to develop. As a FA, though, I liked him a lot. Big picture, the Colts got an under-25 TE, who was among the most TE's ever at his age, and who has the benefit of 4 years of development.
I think Gesicki will get there, and if Miami is able to keep him around, he should make good on his draft slot. With his physical tools, a breakout in 2019 is possible, and he has the highest upside of the potential breakout picks. But, Ebron is an important example, and Greg Olsen also had a slow start to his career.