Alternate Firearms Availability Rule?

I'm working on a homebrew setting that treats firearms a little differently from the options available in Ultimate Combat. Is there any way to implement the following rules automatically with a check box in the settings like the other rules options? Thanks!

Nearly-Commonplace Guns: Firearms are much more common in this era. Early firearms are still very expensive and can be tricky to wield, but they are readily available. Instead of requiring the Exotic Weapon Proficiency feat, all firearms are martial weapons. Early firearms and their ammunition cost 50% of the amounts listed in Ultimate Combat. Advanced firearms and their ammunition do not exist in this campaign.

Paris.Crenshaw said:

Nearly-Commonplace Guns: Firearms are much more common in this era. Early firearms are still very expensive and can be tricky to wield, but they are readily available. Instead of requiring the Exotic Weapon Proficiency feat, all firearms are martial weapons. Early firearms and their ammunition cost 50% of the amounts listed in Ultimate Combat. Advanced firearms and their ammunition do not exist in this campaign.

Click to expand...

So pretty much this is the "Commonplace Guns" rule listed in UC (pg135) except the cost is 50% instead of 25%. So by turning on "Commonplace Guns" option in HL gets you almost what you want.

Unfortunately adjusting "cost" is not possible without making "new" Things. So you will be stuck making sure your players buy Guns for free and then pay for the gun at the right price on the Journal tab. For the ammo and gunpowder it maybe worth putting those in the editor at the correct price.

Best I can think of.

Thanks, Shadow. You are correct. That makes sense. I just wanted to make sure that there wasn't a way to implement the rule via the editor.