It should be able to load the graphics in multiple layers (both in the background and the foreground of the player, and in a couple layers of each so that i can achieve a parallax depth effect) and play sprite sheets with simple programming by me (both in the player layer, and the background and foreground layers). It should also include a collision layer based on the isometric map, and allow for different visual heights in the game (ie, can create slopes or steps). I can make the graphics for this game, but i need the engine to be able to dynamically size the images used. I don't know which types of images will be best for this, but I am guessing that it would be done using the canvas, and WebGL.
As well, it should be able to load text from external files in XML format and use that text in game as character speech or signs as the game progresses.
Ideally, it will be modular so that I may look through it after and make adjustments and add or subtract modules as I learn more about the engine itself.
It should be as lightweight as possible as the end use may include smartphones, etc.