Kajamba Lion said:
Yep, these work on top of the normal classes, and they should work with normal d20 (I had the same thought last night when I was reading it — they might actually work brilliantly with a Relics & Rituals: Excalibur game I've been thinking of running), although they'll ramp up the power level of the group a little bit. What they might do nicely is allow characters to achieve epic tasks without having ridiculous ability scores. My thoughts, at least.
That's exactly right.
The limiting factor, of course, will be the Action Points. Spend the Action Points to do the mythic, epic, heroic things-- without really futzing with the abilities of the base character. It's possible to have a campaign where the heroes are perfectly mundane when it is appropriate that they are mundane, and heroic when it is appropriate for them to be heroic.
Off the top of my head I would say that the Wheel of Time heroes fit into this category. Most of the characters (and the reader as well) don't really realize what they are capable of until the occasion calls for it.
(I could give you plenty of other examples-- I don't even know why I picked on the Wheel of Time except perhaps that it has a very large cast of characters.)
Anyhow--
The GM can control the "wahoo" of the campaign by simply limiting the release of Action Points.
At least one of the Archetypes, The Oracle, really works best on a spellcasting base character or in a game with spellcasting. The other Archetypes can pretty much be fitted to any character class.
What amazes me is how you can sit down with almost any campaign you have played in and, with very little trouble, see which players/characters fit into the archetypical roles. Most folks won't realize they are doing it, but the archetypes are there all the same. We tend to fall into these "shared super-consciousness" roles.
I can't really get too deep into that without the conversation veering pretty deep into Jungian/Campbellian theory.
I do recommend checking out the demo PDF if you need help making up your mind.
http://www.badaxegames.com/mm/pdf/Mythic Heroes demo.pdf