OP needs to hire Computer Engineering grads, not Computer Science grads.
Like you said, that background does have a lot of benefits. But the downside is that a CE grad typically spends less time doing "software" work than a CS grad. When a CE student is taking courses on circuit design, FPGAs, and CPU architectures, a CS student might be taking courses about databases and concurrency. I don't think I touched SQL or a multithreaded program in a university course. Those were all "high level" things that CS students focused on.
This isn't meant as a knock on CE grads -- I just don't think it's wise to suggest them as the solution to OP's problem since they have their own set of "blind spots" to deal with.
Anyone who can figure out timing in a complex digital circuit can learn how threads and mutexes and message queues work, but there’s a good chance a CE grad would not be able to speak to those topics very well compared to a CS grad.
Again, this isn’t a criticism of CE. I just doubt OP would have their socks blown off in the areas they mentioned if they started interviewing engineering students.
My CS degree had digital logic (far too many hours working on Mentor Graphics), machine language programming (from Professor Larus of SPIM fame), compilers (from Professor Fischer), databases (from Professor DeWitt), and networking (from Professor Landweber).
Many classes were cross listed with the engineering department. The ECE degree was much more focused on the "designing a computer" rather than "writing software".
The difficult part there is that some degrees are "build hardware", some are "write software", others are "study the science", and others are "a survey of all things"... and others are "just enough in the business school to write html and do JavaScript."