Actually I think the antebellum militia is often disregarded and given short shift by historians because of the issue that you point to, that so few of the militia colonels wound up commanding units in the war, but I think this represents a basic misunderstanding of the militia system. The antebellum militia laws, all the way back to the territorial days really provided for two classes of militia. Section 1 covers all "able bodies free white males between 18 and 45". In post war militia laws this would be referred to as the reserved militia. It's privates were required to provided their own weapons and no provisions were made for their uniforms and other equipment. In section 57-60, provisions were made for a second class, and actually more important class of militia, the volunteer companies. Each county was authorized to raise up to four volunteer companies. Their elections were certified by the regimental commander, but otherwise they were separate from the first class. Provisions were made for the volunteer companies to be provided with weapons, uniforms and other equipments. This second class of militia would later be referred to as the enrolled or organized militia. In a letter accompanying the printing of the Militia Laws in 1860, Governor Conway calls for the formation of more of these volunteer companies. Examples of these volunteer companies date back to the territorial days, such as Albert Pike's Artillery Company of the 1830s or the Little Rock Guards of the 1840s. It was these volunteer companies that turned out for service along the border during the Seminole War in 1836 and the War with Mexico in 1846. The there are many examples of these volunteer companies being formed prior to the seizure of the arsenal or secession. There are contemporary news paper accounts of these volunteer companies drill up to three times per week, unlike the regular militia that drilled who were required to muster four times per year (1 regimental, 1 battalion, 2 company musters). I believe that the first 12 regiments that were raised in the state were primarily from these volunteer companies, and if you look, many of the regimental commanders of these first regiments had been volunteer company commanders prior to the organization of the volunteer regiments.

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