I usually don't talk about features I haven't already implemented for an upcoming release, but these are two very important features that actually add power to RPG 20XX. These are known as Geo-Mod and Archetypes.

Geo-Mod is the ability to permanently modify a map and for it to remain modified per save file. This idea has existed since the late 90s when FPS game developers wanted absolutely destructible terrain, and they called it Geo-Mod. This enables the development of constructive (or destructive) RPGs with RPG 20XX. This feature came to me when I thought of altering the idea I had for LandTraveller to use this engine instead- giving you an idea of why it is important to have.

Archetypes in RPG 20XX refer to events that can be replicated, like chests, with one or so aspects being changed, like item contained. That part you already knew, but the power comes from the ability to create new and permanent events during the game. In order to create an event, you would need to specify the archetype and the arguments (item contained, other parameters, etc.). Created events can then be persistent and remain on the map per save file.

For commands that target events, there will be "This Event", "Player Event", and "That Event" for any events just created using the above feature in case you wanted to quickly modify the event's other properties (like character set and such).

These features make games like LandTraveller possible, or you could use them for more simple things like terrain that is meant to be modified according to the story or a town the player can build (a staple of many JRPGs even ones from the 90s). The only drawback is that modifying a map increases the save data by the size of the original map. Creating events not so much, though a runaway event creator might overload a map requiring a reload of an earlier save to fix, so be careful when using event creation commands.