Is it right to set a percentage for a director?

Question

Project management

For the first time, I encountered a situation where the customer offers to work on the principle of lead generation. when the performer is responsible for leads and his duties include both the creation / refinement of landing pages, and the development / maintenance of the advertising campaign in Yandex and Google.
In this case, the payment consists of 3 parts.
1 part . Tasks for technical refinement/rework of landing pages (which are essentially service pages of the site). Here the wishes of the client are painted, and mixed with wishes such as increasing the conversion from 4 to 5%, etc. And all this under the pretext that all this affects leads, which means part 2.
2 part . Grid of leads with a target indicator of
50-70 - 5000
rubles 71-120 - 8000 rubles
, etc.
despite the fact that the plan is 150 and the maximum bar includes this plan
3 part . Static, something like a salary
So, summing up all these indicators when running a campaign for 4 services - 6RK in direct and 1 in adwords, the amount obtained when this plan is implemented is average for the salary of an ordinary employee.
How relevant are these prices at the moment.
We have been working with the client for a long time, and there were other grids where the benefits were visible.
Immediately, because of the interest, there are many doubts whether it is worth taking.
I know many people work mainly on an advance payment with a static amount like 15000/5000 for the conduct of the Republic of Kazakhstan.
How are things with you or how do you work with a complex of services?
Thanks