If a player want to "uplift" a particular substance as an elemental, all the GM has to do is decide what the effects of that substance would be, then use the basic elemental patterns to set details:
- AC 2 for all
- HD based on conjuration method (spell = 16, device = 12, staff = 8)
- base damage 2 dice, 1 die for gaseous/liquid forms
- add 1 die damage when attacking in specific arena
- Move based on elemental they most resemble
You could do something similar with the "magic giants", but I'll save that for a future post.