I am not a bad system designer.  Were it not for my love of circuit design, I might well have chosen this branch of engineering.  My system design input has been useful to my design teams in terms of  EMC compliance, DFM (design for manufacturing), power system design. 

This is often very cheap insurance.  Getting a system sketch from a couple of different people can cost a couple hundred dollars and save tens (or even hundreds) of thousands of dollars. 

This kind of work can be hard to estimate.  Let me know what your system is to do and let me see what I can do for you.  I will try to make a fixed price quote (in line with all analog-guy.com projects), but may have to work to a time and materials or capped time and materials budget.