custom potions into villager trades

You have the option to add villager trade element and choose the profession. You choose the element for sale and price(1 emerald for the bottle) and rank of the villager

I think you will need to edit the code of the villager trade (and make sure to save and lock it afterwards), that way you add your potion's nbt data to the item that is sold.

However, I'm not quite sure what nbt data you will need to use, or even what the code for nbt from a villager trade would look like. My recommendation would be to use a tool like 7zip to look through the data files for Minecraft or a mod, and try to look at how the fletcher villager handles tipped arrows.