Expertise with Weapons?

[Nagog]

So a friend of mine brought up an interesting point the other day: if Rogues (and presumably Bards, but rogues state it specifically) can gain expertise in Thieves Tools, how unbalanced would it be to allow one to choose a weapon or weapon type to gain expertise in? Considering Skill DCs are typically in the same general area as AC, I don't think it would break anything as far as that goes, however rolling to hit an AC comes up a lot more often than rolling to hit a skill DC. With this in mind, how would applying Expertise to weapons as a homebrew/houseruling change the game?

[Lord Vukodlak]

Very that’s before you consider stuff like sharpshooter.

[Nagog]

Very that’s before you consider stuff like sharpshooter.

Valid point, it appears that it was set a 5 because that's just under the max proficiency bonus. But all things considered, since expertise still scales with Proficiency, it would still take some time until a -5 to attack rolls is negligible. How would that shape up against other powerful combos?

Just playing devil's advocate here, I don't think I'll implement such a feature, but in fiction it would make sense for a veteran fighter to have one weapon or weapon type that they're exceptionally good at, moreso than one who has never wielded such a weapon.

[Misterwhisper]

Crazy op.

The gap of to hit in 5e is pretty small. At level 1 having a 16 in the attack stat and proficiency is a + 5 to hit.

If you max the stat at 20 and have topped out proficiency of + 6, that is only an 11.

One of the main reasons archery is so powerful in 5e is that their fighting style gives +2 to hit, which is massive at low levels and continues to put you far ahead on everyone else all game.

Magic items only go up to +3.

No magic items at all you could have a to hit of 17 with no fighting style, 19 with archery, and if you do get a +3 magic weapon by then that is a to hit of 22. That hits the tarasque on a 3, and his all but like 4 critters in the game on anything not a 1, and only then because a 1 auto misses.

That is crazy op even as a capstone level 20 ability or an artifact.

[Zetakya]

As indicated, you're into Legolas level never missing territory with that kind of ability.