I left low-sec / FW because it was very empty unless you want to sit in novice plexes in a T1 frig waiting people in faction / pirate frigs to arrive to gank you.
Limiting certain plexes to small gangs would be a great idea and could be easily done. You just have to let a max of 2 gangs/fleets into the plex, and anyone solo or not in a fleet would count for 1 gang by themselves.
Using kills for capping is unfortunately exploitable, and also it means you can’t cap unless anyone turns up to fight you so you could be waiting forever. Personally I would like to see cappable points restricted to a “front line” of a handful of systems (like 2-3), so that everyone in FW is concentrated into one area where there will be tons of fighting. Right now the small number of people in FW are spread very thinly.