The way I look at it, the best course of action, is
1. Get Romo, cut Weeden, June 1st cut Os, retain Savage as the backup, and draft a QB in the first three rounds. Tough to say it as a cowboys antifan, but Romo is criminally underrated. His issue is health, but when he has played, he has played extremely well, any of his seasons between 2011-2014 season would be better than any season any QB has had in our franchise history. Health is the issue, play is not. Yes it is a roll of the dice, but you can hit big. If you assume there would be only a 25% chance he's healthy for he playoffs, that would still be our best chance to get the title. There's reason he has the 4th highest QB rating in nfl history, and if you look at his play the back half of his career has better numbers than the first. If he plays he definitely has something left. Also if you acquire him, Savage will get his shot in a few games undoubtedly when Romo misses time so it wont be as if you have completely given up on him. Throw in a rookie draft pick early in the draft to groom and possibly challenge for playing time later because of injuries or whatever.
or
2. Get Cutler, cut Weeden, cut Os after June 1st, retain Savage and draft a QB, same as before, however Cutler is not nearly the QB Romo is, but with this Defense the team can still win and go far. If you stay conservative, the Brock game plan so to speak, Cutler can win games, also you know what you are getting with him. You can limit his mistakes, but he has much better physical tools than Os and even his bad seasons were markedly better than what Os put up last year. So with Cutler, you lean on the D to win games, with a run heavy offense that takes shots.
Bottomline you have no chance to win with Os, he is just too limited. You can improve the line for sure and add more weapons, but it will be easier to go another direction. This team can win now with average Qb play.