When we played Nap Black Powder don't think we had any major problems with the rules handling large numbers of units and figures ( roughly 1000 plus per side), took a full 2 days gaming, very enjoyable and hard fought.
Must be honest I can't claim any credit for the re-modelled Airfix farm as I bought it off Ebay.
My usual set of Napoleonic rules are "Battles for Empire " by Buck Surdu dating from early 1990s, they have , for me, a good period feel about them and they handled some really big battles, Waterloo, Borodino, Austerlitz fought with local lads over a week-end in a school hall using 50 x 6 feet table, I was umpire, ended up with massive head-ache afterwards
Favourite rules for other periods
"Fire & Fury" and various variants of these like "Age Of Honour" but I don't like the Napoleonic version, personal choice,
"Patriots and Loyalists " for AWI
" Warfare in the Age of Reason" for SYW, although " Age of Honour" easier to teach as most of the lads I game with know "F & F" well.
Never found a Colonial wars set of rules that I'm happy with, anyone got any suggestions??
ECW/30YW I use several rule sets, all which give a good fast game
WSS/GNW, again "F&F" variant "Age Of Honour"
Probably won't be posting until Monday as just about to be invaded by 5 (all over 60s hooligans) on our twice yearly get together, involving slap-up meal in our favourite Bistro, followed by several beers until early hours, then back home for a card session (you name it we play it), we've been doing this since our early teens, which is close onto 50 years !!! Scary or what??!!
Boys just phoned, got to get kettle on, warm up embrocation, more on Monday if I survive.