NO NO NO! Do not explore other options. If you really want to prevent the people from cheating- server side is the way to go. You can't trust the client. Never. The server must be the authority. This is achieved with client-side prediction (since Quake 1, running headless on the server) plus lag compensation (since Counterstrike). Every AAA game and every serious web game is doing this. Server time is cheap nowadays, so you can do this too. If you're serious about your game - talking about thousands of clients make me feel so - then you have to protect the reasonable players from the cheaters with this industry-proven technique.
Read those documents and you will get the hang on doing it on the server.
1. A famous read from 2001 by Bernier, an engineer at Valve. I love this piece of science. You will read about client side prediction and lag compensation in context with other parts of a game.
2. The young Carmack writing about client side prediction:
3. I just love this fact. This is again Carmack about a network ping which is faster across the atlantic than the LCD refresh rate.
4. And a very good multiplayer guide with node & socket.io.
How you can achieve this whole networking with Phaser & Phaser Headless? This is another question.