I already hired engineers for several companies of very various sizes, and I can understand the value you're bringing. This said, if you're only going to be a technical filter, some companies will put your services against a combo of "recruiters + codility".

I personally went through codility myself for a company, and I found it decent, even though it has obvious disadvantages because of being online.

That said, if you feel like targeting bigger companies, I believe you should introduce yourself (or whatever company you're building) as a recruiter, but a strongly technical one, and then adapt your business model this way. It will scare companies less (newness equals risk), and it will make what you're bringing on the table more clear. Your value is in your technical skills.

I understand that the difference in your offering is that you're not offering companies to find candidates for them, but this is where you would become more useful than a method consisting of sending all the candidates to a service like codility.

All in all, I would use your services, but only if you solve a problem that my current tooling (recruiters I deal with, and online filtering services) can not solve, which does not look to be the case if I look at your current proposition.