One of the aspects of 5e that I see the most complaints about are the feats that give +10 damage for -5 to hit.
By changing the wording to allow a player to choose the level of the penalty to hit, limited to a maximum equal to the character's proficiency bonus, and gaining a bonus to damage equally to twice the penalty it seems that some of the bite could be taken out of these Feats.
For example, a 1st level character with a +2 proficiency bonus could only choose between a -1 to hit with +2 damage or a -2 to hit with a +4 damage. At later levels you just continue the progression up to the proficiency bonus.
The DM could choose to cap this at the -5/+10 or allow a character with a +6 proficiency bonus to go up to -6/+12.
If the bonus to damage is still too high, then maybe limit it to a 1 for 1 exchange.
By changing the wording to allow a player to choose the level of the penalty to hit, limited to a maximum equal to the character's proficiency bonus, and gaining a bonus to damage equally to twice the penalty it seems that some of the bite could be taken out of these Feats.
For example, a 1st level character with a +2 proficiency bonus could only choose between a -1 to hit with +2 damage or a -2 to hit with a +4 damage. At later levels you just continue the progression up to the proficiency bonus.
The DM could choose to cap this at the -5/+10 or allow a character with a +6 proficiency bonus to go up to -6/+12.
If the bonus to damage is still too high, then maybe limit it to a 1 for 1 exchange.