Swapping Reckless Attack for Weapon Mastery

We just tied up a 3 year campaign and are starting a new one soon. There isn't much enthusiasm for buying new rulebooks, so we're mostly staying with 2014 rules, with a couple of adoptions from the 2024 set. One player, with a barbarian character, has expressed an interest in weapon mastery. I can't give it to them without giving it to everyone, which would be a huge homebrew effort, which would then pressure people to maybe buy the new rules. As a compromise, the player suggested trading their reckless attack feature for the weapon mastery option so only they had to deal with it.

I recognize this changes the class somewhat. It kind of siphons away some of the unbridled fury barbarians are known for and makes them a little more like a low calorie Battle Master with rage bonuses. Other than that, it looks like a fair trade, but I thought I'd throw it out there and see what other DM's thought of the idea. Is it a roughly even swap? Too big a boon or too huge a penalty? Am I missing something fundamental?