Cutting your gym in half for 'big' and 'small' wouldn't work on so many levels.
1. From a business sense, all the guys under 200lbs are gonna get sick of being stuck with shitty weight dumbells and go to another gym, so you'd lose all that income.
2. You'd have to buy double the machines to make sure that both sides had enough equipment, or are you saying that the 'little' guys can't use the squat rack / leg press / etc., cos they're not big enough?!
3. I'm only 168lbs, but I use the 70lb db's, so what would I do? I also use the dipping bar, pull up station, which 90% of guys over 200lbs won't touch cos they can't lift their flabby arses up.
The only requirement any gym should have is 110% effort. I don't care how big someone is, it doesn't give them the right to more than the next guy. I train harder than most of the guys at my gym, the kind of guys who do one set then take 10 mins rest to talk to someone, load the leg press up with eight plates a side then only just bend their knees while shouting at the 'effort', or laugh amongst themselves when someone smaller than them enters the gym.
Don't forget, everyone was under 200lb at one point, and you wouldn't have liked it if you had been segregated to some corner of the gym with the stability ball and the Pilates class.