I've played a bunch of colonial rules, but always come back to TSATF. If you are worried about fielding the number of figures, use half size units.
I have enough Brits and Zulus to do Rorke's Drift at 1 to 1 Brits (actually a whole lot more!) and 1 to 4 Zulu. Speaking of which, for a Rorke's Drift scenario, I highly recommend Hal Thinglum's rules From MWAN. I believe they are still available for download on the Yahoo "Colonial Wars" group.
I used to run Hal's Rorke's Drift rules for Rorke's Drift and TSATF for refights of other battles or made up scenarios at conventions.
Although I based my figures individually (it is a skirmish type game) I used movement trays to ease moving 1000 Zulus.