You obviously need a Talisman to walk through the Valley of Fire at the end of the game. But if they can protect you from the otherwise impenetrable Valley of Fire, then surely they could also protect you from the Firelands that pop up around the board if the Ifrit are invading. While this makes the fireland tokens a bit less dangerous, it also makes Talismans a valuable and useful resource earlier in the game. Currently, if I get one too early, I just ditch it because they're not all that hard to come by (thanks, Warlock!).

Might there be any unforeseen consequences to adding this rule?

Sounds like a neat addition, though it obviously takes a lot of the danger out of some situations. Maybe you could ditch/discard the Talisman so it's more of an emergency use?

Discarding or ditching may work. I did just realize one complication that would come of this. The Sun Talisman in my Atlantis set won't work anymore. How could do I that to myself?

Fireland tokens are pretty harsh and usually serve as a brutal reality and balance. Therefore I like this usage.