I wouldn’t go for it, here’s why:
You want to maximize your point totals each week. 1 player that puts up 25 ppg isn’t as valuable as 2 players that put up 30 ppg for example.
Lamar is averaging 30 ppg, about 5 more ppg than Stafford.
Hopkins is averaging 20 ppg, and has been on the upside recently.
Ertz is underperforming from what you’d expect, but still at 10 ppg, and could put up more any given week. Herndon is a complete unknown right now, so I wouldn’t be relying on him.
Cook is averaging 25 ppg.
So if you traded Hopkins and Lamar, you’re basically breaking even: -5 ppg at QB, +5 ppg at skill position. Then you’re losing Ertz and forced to play Herndon, which is likely -ppg (let’s say -5). So you’re net value from the trade is -5 ppg. Sure you gain one player putting up big points each week, but you’re losing 3 starters who’s combined ppg are greater.
Cook is one player with big potential, but Lamar, Hopkins, and Ertz can each also ball out any week. If Cook busts or get injured any week, you’re screwed. Whereas say Hopkins busts, you still have Lamar who can ball out, and Ertz who’s steady and can score big.
So whereas Cook may score a lot for you, your team as a whole may actually score less, which does no good. Don’t want to put all your eggs in one basket, cuz if that basket breaks, you’re dead. Remember the sum is greater than the parts.
I know that’s a ton of info, but you want to keep the more steady point potential total. Look at your lineup and see if your starting team as a whole increases or decreases, not just one position.