Half-Life: Alyx playermodels are only part of one of the addons we have and are not integrated into our current system for how OTAs work. We have a rather limited relationship with HL:A content, and I don't think porting Half-Life: Alyx assets one-to-one into the Half-Life 2 game would be effective.
First, we would need to rework the OTA models entirely, which is on our to-do list but, as I mentioned, it's not our main focus at the moment.
That said, I would welcome these weapons later on in the development track.