This is a great idea.  A wide rage of object with varying effects (both good and bad) would really be wonderful.

You give a creative example but I personally would not like to see such a harsh effect on the channeler.  There are lots of good examples of enhansed artifacts (take a look at the 100s of items in Dominions for example).  And it would be great to have the ability to mod your own.

Here is another example-a rather silly one but it would certainly change up the gameplay:

The Ring-if carried by any non-channeler, increases ability levels by 2 (whatever that means).  There is also a 2% chance each turn of the player loosing control of the unit (computer AI takes over).  If carried by a channeler, he/she will have a significant increase in essence (magical power or whatever its called) and gain2 levels in death magic.  However there is a 5% chance each turn that the channeler will loose  the ability to cast one of the non-death magic spell types.  Therefore over time he/she will eventually (despite the best intentions) only be able to cast death magic spells.

-i know, i know, there is all sorts of things wrong with this for a standard game but at least it illustrates how a few well place and well thought out artifacts could really change the flavor of the game.

I am sure super powerful artifacts will exist eventually.  I'd imagine most of them found in dungeons and such are pre-cataclysm (or how else would they get there?)    And there is talk of super rare items  and monsters that you'll only see once in a months worth of playing or so, this likely includes items that make heroes as powerful as channelers.   This would be the type of item that seriously tilts the balance of the game at the end.