Military Oil?

I’m curious if folks have any thoughts on mechanics for equipping units with thrown oil flasks. They’re unusual for a number of reasons - unlike spears and axes they can’t be retrieved after being thrown, and they come in much smaller quantities than arrows, deal damage over multiple rounds, deal splash damage, and may explode in the user’s face. Additionally, fire can ignite terrain and spread, and is a rather painful way to die hence probably not great for target morale. The easiest solution is probably to prohibit mercenaries from using thrown oil (too high-risk, throwing oil requires Adventuring prof, something like that), but for fanatical pyromaniac orcs, the question remains interesting.

My gut instinct would be to start with the spellcasting rules as a baseline and figure it out from there.