Following up to let all of you know that we have fixed the bug with equipping default weapons and have brought the Hard Light Weapon Skins back to the in-game shop. Cheers!
Original Post
Seasons Greetings, heroes. We encountered an issue where Hard Light weapon skins for Mercy, Reinhardt, and Reaper cannot be unequipped. We are looking to fix this issue in a future update, but for now, we have taken the Hard Light Weapon Skins off of the in-game shop and will bring them back for purchase at a later date.