Hi!
First off, I suggest you post a new proposal for the new spell (freezing hands or whatnot).
You do this by starting a new thread with the proposal category.
Second, the energy substitution feat is non-srd so it is not admissable.
You could, however, use the following ENworld specific feat:
Energy Manipulation [Metamagic]
Benefit: You can alter a spell so that it utilizes a different energy type from the one it normally uses. This ability can only alter a spell with the acid, cold, fire, electricity, or sonic descriptor. The spell level of an energy manipulated spell depends on the energy type being utilized.
Cold, Fire, Electricity, Acid Base spell level + 1 Sonic Base spell level + 2
If the original spell was not subject to spell resistance then the modified spell is also not subject to spell resistance.
Examples: Burning Hands (1st level [Fire]) changed to [Cold] is a 2nd level spell. Burning Hands changed to [Acid] is a second level spell, but is still subject to spell resistance. Burning Hands changed to Sonic is a 3rd level spell.
Acid Arrow (2nd level [Acid]) changed to [Fire] is a 3rd level spell. Acid Arrow changed to sonic is a 4rd level spell. All variations of Acid Arrow are not subject to spell resistance.
-Created by SlagMortar