If it's possible I'd rather see a plugin where the client side handles all of the game logic
I'm afraid in practice this is not a workable idea. It's very tempting because it could do a lot to simplify the design of multiplayer games in Construct 2. The reason it wouldn't work though is because cheating would be totally rampant.
If you trust what the client tells you it's done, it could take a mildly technical person a few minutes to figure out what packets are sent outbound when you shoot someone (or complete some objective), then create a keyboard shortcut that does it over and over again (e.g. one key to kill everyone in the level instantly). In short, if your game reaches any level of popularity whatsoever, it will promptly be ruined by widespread unrestricted cheating.
While you could risk this yourself with your own plugin/networking architecture, we could never officially support a system designed that way. Anyone who tried to make a serious game would get totally burned by it, and we don't want to be responsible for that happening.
Since server-authoritive models run the game on the server, basically only user input is sent from the client. So cheating is instantly reduced to automating what are legitimate inputs to the game, which in theory a real human could be inputting to their computer anyway. This usually can only provide a slight edge, rather than totally owning a game.