I would not pick Tua. Putting him behind what passes for an offensive line on the present team would be setting up a shooting gallery in our own backfield. The offensive line needs rebuilding. The defense also needs more than a little help. We have a goodly number of draft picks with which these two areas can begin to be addressed. More than likely, we are not going to win the division next year even with good additions in this draft and FA. But, if the O-line play and defensive play improves, we can find a QB later without worrying as much about him looking like a smashed squash in the backfield...... I know, I know, I am as tired of the Dolphins looking like refugees from the Old XFL as the rest of you - and I am 70. But forcing a brand new quarterback into a shooting gallery is NOT the way to success. Putting the rest of the team into some semblance of 'good' and then finding a QB to fit is the more likely to succeed in the long run than putting an already small QB behind what we have for an O-line [58 sacks last year!].
When you don't have a QB and are in position to draft one, you have to take him imo. Just saying we can find a QB later isn't really an accurate assessment of how tough it can be to find them. We won 5 games with one of the most talent-devoid rosters in the league. Next year is a complete toss up as we start to add talent, don't take the risk. Don't forget we have plenty of picks (even with a trade up) and cap space. We will absolutely not be going into next year with the same OL. We can - and must - be able to address multiple things effectively.
I am just not sure about Tua... He is not a large individual, and has already been injured. He may come back just fine, but in my eye, he is not built to withstand what is going to happen in our pocket next year. Even if we draft and hijack some OLineman in Free Agency, Tua is small. Defensive linemen and linebackers at this level are going to be a problem. My concern is how long he can stand up to the pounding the normal NFL QB takes - and if he can't - what do we do for an encore?
While there may be some worry regarding the injury long term, there really isn't anything to indicate short term issues, nor is there any real indication that size will matter in regards to injury either. If we are wrong and he can't stay and/or flat out sucks, we at least took our shot and we will then take another. It's what you do until you find one.