Exactly what I was thinking, but of course as I'm not experienced with this I thought there could be some glaring issues with it.
I would love to see some data (even if anecdotal) from someone that tried something similar. Imagine that you can even treat some of your older, most successful employees as "passive income"; as a recruiter you made a really really good effort locating, training and making the best fit for someone, and then that someone is netting you, say, 1% of their salary every 6 months or something, for the next 5 years (haven't worked through the numbers so that might not even make sense), but replace 1% and 5 years with X and Y.
In general terms, I would like to have a recruiter in more "closer" terms. So maybe this recruiter got me a job at company A, then 3 or 4 years from now, since they really did their job and know me well, they can put me in a much better job, for say the next 3 or 4 years again, and so forth. That would mean both he and I could have continued income due to the effort we both made. He made his effort picking a really good candidate and so did I, doing my job.
Kind of like an investor. Successful traders are usually the ones that make their due diligence and thus are rewarded with the most handsome payouts. Isn't that what a recruiter should do? invest in a particular candidate and find the best place where his "investment" can payback handsomely?