There are several ways to go, but I thought MySQL would be an easier method for the first dive. While I was doing my research on the matter I found
RMXOS which allows for good communication between the games, but is based on the client-server principle much like Pokemon Essentials: Online and NetPlay, hence requiring its own server
GUI. From what I've read, it allows for differen kinds of data sharing between RMXP games, so it could be tweaked and used within Essentials. I'm not 100% sure right now, but these were the general impressions I got. But like I said in the thread, this method would require a dedicated machine to run alongside the game, which I know I wouldn't want.