Every team must expose at least two forwards (and one D) under contract for 17-18 (right don't suffice) who meets the 40/1,70/2 rule.
Mitchell and Martinsen meet the rule and WILL be exposed.
M.P, P.B., P.D., A.G., B.G.
That's five guys that are absolute locks to be protected (the only way they aren't protected is if they're traded). And there are quite a few players between those five players and Mitchell/Martinsen, starting with the obvious Alex Radulov if he has to be protected. If not, well, there's still Plekanec and Shaw. And even Hudon for all I care (who doesn't meet the criteria above but is otherwise not exempt).
Bottom-line : Even if we end up protecting both Plekanec and Shaw, we'd satisfy the requirements as far as exposed players are concerned. Hell, any combination of Plekanec, Shaw, Mitchell and Martinsen would work. Flynn doesn't have to be signed for that sole purpose, unless of our our players that need to be protected is traded for an exempt player, in which case we might be stuck protecting three of Plekanec, Shaw, Mitchell and Martinsen (and if it comes to that, just protect Hudon and you still have two players who meet the criteria without having to sign Flynn, or Radulov if you want to go absolutely by the book.)