As a DM, would you let your players change the ability score increase they get from a feat?

Hello, everyone. I've been a DM for seven years and started a new campaign a few months ago using the 2024 rules. My players had just reached level 4 and were choosing their feats. However, the party's warlock (who is using a melee pact of the blade build) asked me if he could get the Great Weapon Master feat, but instead of increasing his Strength, he would increase his Charisma. I said that I would think about it, and now I'm here asking for advice. I don't see a problem in this case, but if any player could do this to get any feat and just pick whatever ability score increase they want, I can see them becoming a very OP group. So, what do you guys think?

Edit: Thank you guys for the feedback. It seems most people agree that I shouldn't allow the changes in the ability score, and I'll follow that advice. Just to answer some of the comments I saw, the warlock has a Strength score of 13, the minimum needed to use a heavy weapon without disadvantage, and he wields a greatsword. Since he has the Pact of the Blade invocation, he uses his Charisma to attack and damage rolls using his weapon.