I also like the idea of a Negro League TA. Even more than that, I like the idea of a Negro League or integrated old-timey mini-season. Only old-time stadiums, uniforms, and old school/negro league players.
Maybe it's too much to ask, but it would be cool to have a random player generator in honor of the many athletes lost to history. It would add a nice "unknown quantity" dimension to the mini-season format (a taste of baseball before information saturation?) and would save us from contests against the same players across multiple clubs.