Yeah, I opened a door I shouldn't have with Red in Magic. As Red is also the colour of Haste, Pumping Attack Only (Firebreathing etc), Doube Strike, Artifact destruction, Temporary Change of Control (Madness) etc.
That latter associated effect is an example of how Magic took years to to fine tune the scope of each colour, Ray of Command was a Blue temporary Change of Control but blue had too much utility goodness so they turned it red. Magic made loads of mistakes in the early days, so many Restricted and Banned cards. Mage Wars is a paradigm of consistency for the same age maturity.
Fire has more uses than just blowing things up or setting things on fire to watch them burn, and I think that should be embraced. Using fire in the game in a way that mirrors how fire is used in real life (and would be used in daily life in Etheria) is, to me, entirely consistent with what fire is. I've always thought that games that view fire as only destructive are selling fire short of all of the awesome things it can do.
After consideration, you have won me over to change my position. Not because of theme (a Forge does not create Leather Gloves, Boots, Cloak etc.) as Forge is just a mechanic. More because I like its "Flame Immunity. Hydro +3" traits which does make it hybrid War/Fire.
I do agree about Fire being typecast. Cauterise and Forest Fires are other examples. The D&D Druid specialises in domains from Animal / Plant / Earth / Water / Air / Fire. Latter because Forest Fires are often good for nature. It clears out the deadwood so that Nature can start again (this is not a second edition reference).