what if simon got really bored (not that thats likely to happen) and created an element for every item on the periodic table (at least the ones where you dont need a Ph. D to figure out what it does) that would be pretty awesome.
Also, I think that there should be radio waves/x rays - that sort of thing so you could have "wireless" receivers,
also, there is a game that used to be prety fun, but pt is so much better, anyways, its called dust or the powder game, and was created before the original pt, the website is http://www.notdoppler.com/frame/639.html
not all the things on there are great, but some of those elements (with some tweaking) should be added to pt
one last thing. last summer, i got bored and created a program that scans a bitmap (or other picture) then depending on the color, saves each pixel as a certain number in a text file. pt should have this ability (scan a picture, transform colors into elements, maybe scan a second and third picture for pressure and heat overlays, than allow the user to do whatever with it in pt. maybe also have a reverse of this so you can save items locally as bmp/png or even txt files
What about inert gas? It would be useful as it wouldn't catch on fire and if we make it as nitrogen it can come as a result (relative term lol) LN2. water vapor would work but only if the temperatures were greater than 100C, this would only require temperatures greater than -196C. Just a thought.
Why were bullets deleted in these new versions of powder toy? can we have them back? can we also have virus? it eats and takes over any solid or liquid particle and replaces it. also flammable. there should also be some more elements. be creative and think. how about laser? or bullets that only travel in straight lines?