Eh, so it can go both ways here. Arguments can be made from everywhere on this one.
My personal opinion below.
So while I think it's very healthy to have a limit on the amount of police that can go on duty, until improvements can be made to the system in general, it is probably better off gone for now. A couple examples of what I mean:
It's currently clunky
You'll be able to load into a blufor slot and hit okay to enter the game, but you'll be hit with the cop limit message.
Potential Fix: if you are able to click an empty blufor slot to fill it, you should be able to load in. The slots change every so often based on population, I think that is good enough.
Cops on duty
As it stands, cops currently have to lobby out to be able to redeploy to federal events. Currently, federal events are a tad borked. It can get hectic at times for the cops on duty to respond to them all.
Potential Fix: teleport options for federal events to prevent the need to lobby out of the game to respond to the federal events.
These are just a couple of my own thoughts on the issue. I'm fairly indifferent to the limit.