10 USC 246 already covers the entire male population (at some point in their lives) as well as some specific females. There is nothing preventing Congress from opening it up to the remaining females. That is concrete, tangible evidence to support my interpretation.
The Federalist Papers, specifically #29, discuss the militia as being comprised of “the great body of the yeomanry, and of the other classes of the citizens”. It refers to a “scheme of disciplining the whole nation”
While most of the paper discusses “the formation of a select corps of moderate extent, upon such principles as will really fit them for service” (aka: The National guard) it also discusses militia obligations on “the people at large”:
Little more can reasonably be aimed at, with respect to the people at large, than to have them properly armed and equipped; and in order to see that this be not neglected, it will be necessary to assemble them once or twice in the course of a year.
Congress does not see fit to maintain such assemblies today, but they did exist back then, and they could be reinstated at will tomorrow. Any member of the “people at large”, is thus also a member of the militia.