I'm a recruiter. Before that, I was an engineer for 5 years. What you're describing sounds really good, but it's likely not going to happen. For the record, I agree with you completely and try to work in the manner you describe, but there are a number of economic incentives working against you before scale is even an issue.

Generally, recruiters work for specific client companies and try to fill seats at those companies. Because the companies are paying them, their interests are fundamentally aligned with them and not with you. The kind of recruiter you describe is more of a talent agent, but until there's a shortage of engineering jobs, this probably won't happen for full-time roles because the financial incentive for engineers to pay an agent simply isn't there.

Agents make sense when it's hard to find a job or when the opportunity cost to looking for work is high enough to justify paying someone else. Recruiters make sense when it's hard to find workers or the opportunity cost of looking for workers is high enough to pay someone else. In some sense, it's almost like recruiters are talent agents for the companies they're representing.

Freelance engineers do have talent agents (e.g. http://www.10xmanagement.com/). When you're a freelancer, your time is split between doing actual work (coding) and drumming up business, so the less time you spend on drumming up business, the more time you can spend doing work that pays. In this model, paying someone to find work for you makes perfect sense because the opportunity cost of not working is high enough to justify the payment.

Full-time engineers are a different story from freelancers, however. I found this out myself when I first started my own recruiting firm. At the time, I really wanted to explore the talent agent model. This model was really interesting to me because I was convinced that having engineers pay for an agent's services would swiftly rectify many of the problems that run rampant in technical recruiting today (e.g. wanton spamming of engineers, misrepresentation of positions, recruiters having a very shallow understanding of the space/companies they're recruiting for).

I dedicated a good chunk of the first few months of running my business to talking to engineers and trying to figure out if a talent agent model would work. Engineers were super excited about this. Until I mentioned that part where they'd have to pay me, that is.

These days, I try to work in this weird hybrid way where I start with finding smart people, figure out what they want, and then no matter what it is, try to give it to them, while still getting paid by the company. This works for me because I maintain relationships with a lot of companies at once. And it also works for me because, as a former engineer, I can grok what people want at hopefully a deeper level than non-technical technical recruiters and also be able to filter talent somewhat effectively.

This still isn't ideal because my incentives are still kind of misaligned and because companies don't always love this approach -- it's great for candidates, but from their perspective, flow is unpredictable and haphazard. And I think this model works for me primarily because I used to code.

So, tl;dr, while what you want sounds awesome, and I want it too, I don't think it's going to happen in any real way anytime soon. At least not until a product comes along.