(When you use the input common-mode range as spec, you mean that you use the "hand calculations" to reach the point where thy leave their saturation regions?)
Anyway, depends on your application, I would focus on the overall specification in terms of eg gain, bandwidth, phase margin, current consumption or what-have-you. Just push the transistors as far into subthreshold as you can while meeting the specification. You also know that S3=S4=kS6 and S5 = 2kS7 also in subthreshold. So not that many parameters to sweep.