It sounds like what you want is Mishegos [1], described here [2]. In fact, this work shows that Capstone performs rather poorly compared to more permissively licensed open-source competitors such as Intel XED and Zydis. Really, if your focus is x86, then Capstone is not the right choice. If you need cross-architecture support, then perhaps Capstone is the right choice.
Yes, that's half of what I was suggesting!
With a little bit of additional work, Mishegos could also be used to test x86 Assemblers... and/or to "pit" x86 Assemblers vs. x86 Disassemblers...
But anyway, excellent links!