I may be wrong, but to me Draconis Combine always appeared to be quite centralistic.
Coupled with House Kurita's fascination with the ways of the Samurai I believe that the Draconis Combine militia units are assigned a military officer by the DCMS. Either as as an aide to the actual commander, or in my opinion more likely, as the commander of the militia unit in question.
Assignment to such duties would also probably be unpopular with DCMS career soldiers and might be a punishment for officers that embarrassed their superior, or just lost ther superiors favor.
Regarding style and organization I agree with your assessment, Takiro, that their is likely great variation among the Draconis militia units as the quality and quantity of equipment that a militia unit can acquire depend in my view largely on how affluent a world is. Prosperous worlds can in all likelihood assign a larger budget to their militia unit(s) than poor worlds and thus build more and/or larger and/or better equipped units than worlds struggling to get by.
Just my two cents.
Ciao
Hessian
P.S.:
If a DCMS military officer is assigned only as an aide to the actual commander, I assume that this commander would either be the planetary chairman or a representative of the planetary chairman.