how can i simulate nocollisionconstraints on client?

I'm trying to make pretty much an antifling script on client (so the server can handle more) and i don't want to mess with replication. My solution is to simulate nocollisionconstraints (basically make other players parts not collide with only the local player's parts) because you can't really use collisiongroups for nocollisionconstraints. I don't want to use .cancollide because if the local player has network ownership of a part, and the other player hits it, it wont move. messy stuff. How would I do this?