That post if you kept reading was up for debate if you kept on reading were basically following three core rules when deciding powers:

An element must be absorbed before we can use the associated power

The properties of that element must have matter or traits consistant with said matter

No OP, over abundunt powers like air, water etc and no time travel :) 

Obviously these are unspoken hush hush rules but they are pretty much what is stated throughout the thread.