Would all melee PC attacks doing alignment damage be unbalanced at low levels?

For a campaign, I am currently discussing giving the PCs the ability to convert all melee and unarmed damage into alignment damage instead of normal physical, slashing, etc. damage.

One of the players suddenly realized that that makes the attacks extremely powerful and unbalanced at first level and lower levels.

Now I am wondering: is there anything I have overlooked that means having this ability starting at lower levels or level 1 could unbalance things in a normal Golarion campaign?