What you describe sounds similar to affiliate marketing [1]: Post a link to external services and get commission for clicks (maybe depending on conversion).
Or some other way to deliver ads with copy and images, but through the backend. (that way the website author has complete power on what an ad actually can do on their website)
This is the major reason ad networks put JS on publisher sites. You can't give a website author "complete power" any more than you can give an advertiser complete power.
The problem with affiliate marketing is that you must trust the advertiser in reporting conversions and paying. You can trust Amazon and some other businesses that way, but not a small business.
In most affiliate marketing programs the advertiser doesn't report the conversions - tracking and payment is handled by the affiliate network as an intermediary, which has it's own pros and cons. But they will fight for affiliates when commissions are due.
DM me if you'd like to talk more about that, I work in the industry.