The problem with developing QBs is that, no matter how much you like the player, so much of the actual development can't happen until after they get in the league and after you start giving them valuable snaps. The snaps in a lot of ways are as valuable as the draft picks. The other issue is that about half the teams don't really have adequate starters, and they have GMs looking not to lose jobs, and so they tend to overdraft any player with the measurables to potentially play the position. As jterrell suggests, it's expensive paying that sort of premium every year or every other year. With reps at a premium, too, you barely get a chance to find out what you've got before you have to decide whether or not you're going to keep it.
Like with any position, the best policy is to churn as much as you can at whatever rate lets you fairly analyze the players. For QBs, that churn rate is not very fast, unfortunately. Which means you have to be relatively selective in who you're going to give the reps to. So you do what you can. You bring in extra guys in camp, and you cut quickly the ones that don't show you the physical traits you want at the position or who don't have the mental makeup you're looking for. You carry three QBs, if you can, so have an extra slot to try to develop one and to create competition. And then you get them in the film room, or using the new VR systems, and you create as many situations as possible to give them reps to develop. But it gets expensive quickly if you're wrong.
For that reason, I wish we had spent a premium pick somewhere along the line on a young QB we thought could take over for Romo when the time comes. Or we found a younger guy we liked on the scrap heap. I've got nothing particular against Brandon Weeden, except that he's old. Those Wed snaps he's been getting the last two years are gold, and they'd be better spent going to a younger player we're hoping to develop. That's doubly true if those reps pay off and Weeden starts to look good, for the record. Somebody like Tom Savage, who we were reportedly interested in in 2014, might be a good example. Get a talented young guy who meets your physical and emotional requirements. Give him some competition to push him to make the roster, and then give him the reps he needs and the protection and the weapons he needs to really develop.