Trying to balance the colors in Brit-like games

I recently played the Diceless Barbaria prototype solo, as well as several scenarios of Frankia (also diceless).

I used to try to play early prototypes as though each nation was independent. I wanted to see what were the most natural moves for each, and try to arrange the game so that the most natural moves matched what they did historically. But I found that this didn't work out when the influence of colors was introduced. So now I always keep in mind the colors I've selected.

I still want the most natural play to be the one made historically, but I have to be aware of how an unnatural play by one nation may help another so much that the game will be skewed.

I'm not really worrying about how strong the nations were historically, I'm worrying about how strong (or weak) they need to be to make their most natural moves match history.

I know that in any game, unless I put a real straitjacket around the player, as in many of the SPI games from back when, the game is rarely going to follow history. What I want is one where I can say, after a player has moved, "yes, that's just what they did historically". I am striving for effect, largely, relying on cause only in the very largest sense--because designing games for cause is a chimera (barring, perhaps, highly-detailed tactical games where you use made-up scenarios rather than known historical battles).

In Frankia, which is a fairly small game (around 30 pieces on the board at any time), I have taken to counting pieces of each color, and areas occupied, after each turn. I'm trying to be aware of what it would be like to play a color: are there times when a color has few pieces and little to do? Sometimes there's nothing I can do about that (as when yellow in Britannia have only the Scots and R-Bs), but I can try to avoid it as I try different nation combinations.