This. This is completelly the solution and the way to go, imho. Goblins with crossbows won't threat High Level PC.I think the best answer is to scale the archers. After all they are not sitting on their tushes knitting while the PCs are out fighting goblins. So it makes sense that they level too.
But Ranger 4/rogue3 goblins with poisoned crossbows? That's another matter.
And if your players don't know which goblins are garbage and which goblins aren't, they will be wary in front of those 12 crossbows. Because yes, if those are lvl 1 CR 1/4 goblins, this is a feast. If they pack 3d6 sneak attack and have favourite enemy human, that's another matter.
4E style won't give them class levels, but will use higher level goblins. They are not "filthy goblins" but "fell goblins" or "killer goblins" or whatever.
This is the solution. Not making 12th level warriors weak enough so anyone with 35gp can buy a crossbow and challenge them.