Yes, I registered just to pitch my crazy idea, because this forum doesn't allow guest posting like the other BG2 mod forums.
I recently decided to give this mod a try, in hopes that it had what I was looking for. It's a very useful feature to say the least, especially since I usually end up with tons of extra gold the way I play. My favorite strategy for BG1 and early SoA is to turn one character invisible, protect him/her from fire, walk into a crowd of enemies, and then drink (not throw) oils of fiery burning. It works like Sunfire without dispelling invisibility. The problem was that until now, explosive potions were quite rare in the game.
My suggestion however has to do with the possibility of allowing the herbalist to brew together existing potions (for a fee of course). Perhaps this could be done in a separate menu from the herb combinations. The combinations would be directly analogous to the herb combinations, so for example a healing potion + sleeping powder = a potion of clarity.
The major combinations I had in mind however had more to do with space-saving and convenience. Specifically they'd let you combine those dinky little healing potions (9 HP) into a potion of extra healing (27 HP) or several of those into a potion of superior healing (40 HP). I think a 10:1 ratio would be a reasonable tradeoff. Also, the Oversight mod gives Sendai 2 drow healing potions that essentially have a Heal effect and restore all HP. Perhaps you could brew 10 potions of superior healing into one drow healing potion, for a reasonable sum of gold.
I know that the Herbs & Potions mod hasn't been updated in a while, so just a thought in any case.