Sir Brennen
Legend
Not exactly. It took you more math to get there.Doh, that doesn't work.
Instead of doing 40 points of ice damage being reduced by Resistance 15 to 25 points, you'd do 20 points of ice damage and 20 points of regular untyped damage which would be reduced to 5 points of ice damage and 20 points of regular damage. For a total of 25 damage, which is exactly as before.

I think some people are using the wrong starting point for the hypothetical Ice Mage. It's not so much about an Ice Mage in the North, because that's a very specific type of campaign. It's about handling an Ice Mage from the North in a regular campaign. Tweaking how resistances work at the North Pole aren't going to do diddly-squat for him 90% of the time in a standard game. Of course, he'll also run into Cold resistant creatures less often, until the upper tiers when creatures with multiple resistances are the norm.
It's about the problem of themed wizards in general, not campaign locations.
I think Fire Mages are a trope less latitude specific, so perhaps the discussion should focus on them.
Personally, I also like resistances. People talk about simple... resistances are simple already. Changing them to a Defense Bonus also seems simple, but it doesn't solve the problem of themed casters, and potentially pushes encounters with such creatures further into grindspace than the original resistance would.
Irda Ranger's idea of Elemental Mastery as a feature of Arcane classes is interesting, but I'm not crazy about having this built-in sameness for all arcane classes. Plus, it encourages such classes to specialize rather than it just be an option. And what if I wanted to have a themed cleric of a Fire god, which uses the Divine power source?
For the themed caster problem, I think feats are the answer, complimented with Paragon Paths, and they're components already built into the game. RangerWickett's proposal way back on page 1 is a bit overpowered, compared to an existing heroic tier feat like Astral Fire (+1 damage for fire/radiant powers). But what about a [keyword] mastery feat which lowers a target's resistance to your powers by 1 for every power you have with that keyword? Another feat which give Resist [keyword] equal to 1 + 1/2 the number of powers you have with that keyword? Lots of other possibilities as well.