You know, I've looked for this for longer than you'd imagine, but still, people here seem to be so reluctant to try anything new aside from the basics, you probably won't find what you're looking for.
If you're as eager to make a multiplayer game as I am, then you might consider just eventing it, or learning to script and save countless lives by actually making this request for the seemingly endless waves of .org users who have requested it.
If you use events, you're pretty much stuck with one inventory, no real battle system, and no equipable armor or weapons for the second player. You might end up with a decent way of using two actors as players 1 and 2, but random battles would be difficult, especially since player 2 can't control their character during the fight. If you DO get something figured out, please let me know. I'd be thrilled to see something come from this.
And good luck!