Two things I believe should be added to this engine:

1) The ability to change a wall's  texture via script when you activate a terminal, in order to simulate things like flipping a switch or pressing a button on the wall.

EDIT: You can ignore suggestion number 2, as the posts below illustrate.

2) The ability to trigger a script when you grab certain objects such as a key (or a way to place a key and a trigger in the same space, either way I want a script triggered when you grab the key).