This looks really awesome TripleX! Fantastic. Conitec must hire you.

Ok I'll fire off my first suggestion. Remember I am not a programmer (yet?)

How about creating to save EasyParticles effects with emitter as a 'package' and place them right in here. For example say in this level I want to have some steam leaks from pipes, some electric sparks from broken cable, leaking water, some small gas flames or maybe some smoke in oven maybe you could create these in EP and save it so that instead of adding an entity and assigning an action each time you could import these in a dropdown of 'particle presets' and the user could point and click and place the steam in a few places, the fire, smoke and sparks etc this is more useful to see in game live when you are creating an enviroment or mood. For example you create a dark alley and you can say hmmmm... this would look much scarier with some rain, click add your rain preset that you had made before in EP, hmmm... wonder how it would look with some steam coming out of the manhole cover .... or you are designing a waterfall and want to add a few particle 'splashes' by a few rocks ....