The lack of fire Pokemon that originated in the Sinnoh region was appalling

[Rainbow Yoshi]

izaaz101 said:
I could see some sort of "Melting" HM being used in an ice region, or instead of flash in caves, you could light a torch with a fire based HM.

The first idea could be incorporated into the Generation V Pokemon games, but the second idea may not as Flash is a more appropriate TM that can be used as an HM.