Even though I highly doubt your first round idea, I honestly would not be shocked if it happened in R2.
However...it wouldn't be Ball (who I think goes much, much lower than people think due to wear/tear). I think the guy they'd run to the podium (in R2) for is...
As much as I like Turbin, he's not Lynch. Not even close. Turbin, IMO, plays like a 200 lb RB who has really nice burst and pretty good wiggle (catches the ball very well too). He can be physical but is only successful when he has a runway (ie a 5 yard cushion between him & a DB). I think Turbin can definitely be a starting RB in this league (and a good one), but he's not the tone setter that Lynch is. Lynch is a punisher. He epitomizes the Seahawks from the 1st carry and doesn't need a running start to make a defender "feel him."
I think Lynch has tread left, but he's definitely a candidate to have a significant drop off (when the time comes). Again, it's not that I don't think Turbin is a starting caliber RB, I just don't think he's what the Seahawks feed off. Eddie Lacy is that guy. The same can be said about SF with Frank Gore. LaMichael James is a really nice RB, but they are a different team when he is in there. Yes, he provides explosiveness, but over a 16 game season, it's the power guys who survive/thrive. And, SF & SEA are built on physicality, power, aggression, in your face, and both teams can be "summed up" by the fact they have very good young QBs, but still are centered around a power run game.
*I'm in no way advocating a R2 pick being used on a RB, but I do sincerely like Lacy (have like him since his limited carries Frosh year) and wouldn't be shocked if they did something like this, knowing that a Lynch type of runner is really hard to find, being since about 3 college programs actually successfully run a power game (Bama, LSU, Stanford) at a high level.