Oh it's definitely risky, but I could see some "forward thinking" GM giving it a shot. I look at Washington did with Kirk Cousins and could see a team going that route, but with a trade obviously instead of letting him hit the open market. He was a good QB for them but they knew he wasn't the superstar that was going to elevate them to multiple SBs, so they let him go. Main idea being that you draft a QB and then supplement with a Ryan Fitzpatrick type of guy. Maybe you hit on that pick and you get a Mahomes or someone like that, or if you miss, you have a fallback until you get a chance to try it again. Just could see a scenario where a team gives it a shot instead of having a ton of their cap tied up into one player.
It won't work, for a couple reasons:
1. After that happens even like one time, the "Ryan Fitzpatrick types" will start commanding $20M per year or more. Look at what somebody like Teddy Bridgewater gets on the open market. Or even a guy like Alex Smith. Nobody really thinks these guys are anything more than stop gaps. Once agents figure that out, they'll start feasting too.
2. I generally find more cap space overrated, mostly because it doesn't translate into winning. The Patriots didn't win all those years because Brady took less... they did very little of anything with the cap space he gave them, which is partially why he's not there anymore. They didn't use the $10-15M of "less" cap space he took to go sign any stud playmakers or give him any help. They won because they had great players at key positions for short periods of time.
I think there's one key things that NFL GM's and HC's have realized that fans generally haven't come around to yet...spending less on players doesn't translate into winning. Spending $40M on a QB doesn't make it any more or less likely that you'll win than spending $20M on a QB does. People show the stats of % of Salary cap and all that, but its entirely based on the only barometer of success being winning the SB, which of course, isn't true.
NFL GM's know that spending $20M less on a QB only guarantees one thing... that they spent $20M less on a QB. Everything else afterwards is just a series of IF statements. IF they use that $20M on free agents, and IF those free agents play good football, and IF everybody remains healthy, and IF the drafted players they extended continue to play at a high level, then, and only then, does it pay off.
NFL GM's don't want to have five or six "IFs" go right in order to just be competitive. They want one IF. IF Patrick Mahomes stays healthy, KC will compete every year. Will they win a Lombardi every year? No, but then again, neither will the "revolutionary" team who goes bargain hunting in the draft. If you're elite at talent evaluation, your stud QB on a rookie deals wins a Lombardi one time.