In Black Powder (and Hail Caesar, its sister game), the bases represent a unit of guys with each figure representing 5-20 guys depending on your scenario. You do not pull figs from the unit as the unit takes damage but place casualty markers next to the unit representing the fact that the unit has lost a portion of men. When the unit takes a certain amount of casualties (represented by how many markers it has), the unit is considered to have been routed, or destroyed enough. Sure there may be the odd man still fighting on the battlefield, but there is not enough men left in the unit to make a tactical difference in the battle. (This game is made to represent battles where thousands and thousands of men fought in a battle, so individual models who are not commanders would rarely make a big difference.
For any historical figures, I would suggest doing what I have done with my AWI (American War for Independence) figures. I am basing them on washers and then am cutting magnetic sheets to the standard sizes used by the various rulesets. This way I can just stick 4-6 guys magnetically on the base that game uses without ever needing to rebase by guys if I change rulesets. This also allows me to use the figs for skirmish games like Ganesha Games' Song of Drums and Skakos which I recommend strongly if you are getting in to historicals as it gives you a game to play while collecting a larger force to play games like Black Powder. You can pick up their rules here:
http://6sided.net/products-2?ap_id=nuadha Song of Drums and Skakos is only $8. It is designed for Napoleonic, but can easily be adapted to any black powder era figures. (I use it for AWI.) They have rulesets that cover any era of Modern Warfare and they are coming out with an ancients set called Song of Shields and Spears. For more detail on how their basic rules mechanics work, you can also check out my review of Song of Blades and Heroes here:
http://nuadha.6sided.net/2011/06/21/other-options-song-of-blades-and-heroes/
For Pike and Shotte, you may want to check out Warhammer English Civil War from Warhammer Historicals. I recently picked up a copy on eBay for only $10 and it is a very nice book. Field of Glory has a rulebook that covers the era as well though I have not been too impressed with the rules.
Automatically Appended Next Post: Also, I should point out that Black Powder does not really cover Pike and Shotte. The rules were written to cover wars from the early 18th century (War of Spanish Succession) to the late 19th century. The main difference is that in the Pike and Shotte era the gun did not yet replace the Pikemen and melee specialized troops. The War of Spanish Succession is considered the first war where most units would be armed with rifles. Of course, the rules are fairly flexible and with some adapting you could probably fix that.
