For what it’s worth, I’d probably be more interested if it was something I paid for. Otherwise, ends up looking a lot like the existing contingency recruiter model.
You can't say you will find the best job for someone and then magic up a contract with every company they want to apply to.
Why would a company pay for a candidate with an agency fee attached when they probably have other similarly qualified candidates that have applied directly.
That puts the candidate that has applied through you at a disadvantage and encourages the employer & candidate to swap details and circumvent the service after an introduction has made.
Whoever requests your services is the one that payment should come from and (from experience) candidates do not want to pay.