As far as I can tell the historical equivalent of pistoliers were the Hakkapeliitta Cavalry (
http://en.wikipedia.org/wiki/Hakkapeliitta).
The greatest advantage of the fast and lightly-armored Hakkapeliitta cavalry was its charge. They typically had a sword, a helmet, and leather armor or a breastplate of steel. They would attack at a full gallop, fire the first pistol at twenty paces and the second at five paces, and then draw the sword. The horse itself was used like another weapon, as it was used to trample enemy infantry.
So I can see why people call for the Fussilade rule. However, in order to make things more comparable to the actual tactics I'd propose the following:
When charging:
Resolve one shot/model on long range (giving -2 to hit. -1 for the charge and -1 for range).
Resolve 1 shot/model on short range. (-1 to hit)
In close combat: Fights with hand weapon. (Rilly the same thing sa brace o pistols).
This charge would not be as overpowered as the Fussilade was, but it'd still fit the unit.