The following is what I had previously posted about rules...
I think that I have finally made a decision on the rules to use for mass battles. After some thought and a few practice games - using just some old metal bases as units - I have decided to use Fantasy Rules! by Chipco. I think the benefits of the quick play and unique army control system, the Morale Clock, outweigh the non-linear basing. I will do some tinkering to FR!, as I think the missile ranges are too long and some of the bases, for ambuscadiers (skirmishers) especially, will be rectangles instead of squares just for appearance's sake.
I will post my rules mods here as I go.
I still have not really made a decision as I am now plowing through a series of AWI (American War of Independence) sets to see if they are compatible. The lack of cavalry in both the AWI (and even War of 1812) and the Half-Continent is a surprising commonality, as is the variety of units possible. So, I continue searching - it will end soon as I am almost ready to base up troops!
Many thanks for The Baron for his suggestions!