I would think flavorings and sweeteners and steeping would reduce harshness. I also believe there are some additives that can be used to smooth out harshness, but I'm afraid I don't know the names of them. It might be worth a shot though.
But, it might be time to see if you can remove the harshness on your own. People convert regular nicotine to
nic salts, using citric acid. There is a thread on it somewhere, I THINK the DIY thread? You can actually measure the Ph as you convert it, but it's overall not that complicated I think. It will take time for whatever agent you use (most folks use citric acid) to dissolve into the nic.
If you do a mix and it remains harsh, that might be an option as at that point, you don't have much to lose if you can't vape the nic.
I started DIY with Nic River's
nic salts. They're excellent and not harsh. When I started out my throat was pretty torn up I didn't WANT a nic hit. I finished stockpiling with regular nic, and I have a feeling I'll be able to vape it now, but if not, I plan to convert it. Nic River's nic salts are great, but not cheap. They do have sales from time to time.
Nic salts are also reported to remain more stable over time. IDK about that, but I will say I get NO harshness using nic salts, nor any kind of peppery "taste."
Good luck!
Anna