Thought for an artifact tweak: How about having the Skin of Many scream (extra loud!) when there's stealthed or invisible units within a certain radius? Probably 2-3 tiles. Maybe nothing but a message ala Prox's Halfling's Foot and traps, maybe something a bit extra as well (reducing enemy stealth/invis power if they're inside the radius?).
Right now, the poor thing is... kinda' boring. And pretty weak, t'boot, with little going for it even for undead (the fear resistance in particular is something of a joke
). Could probably even leave the effect for undead, retool the message/effect a little (screams coming from the nearby air, nice and spooky-like, instead of the armor itself, ferex).
E: Also, full artifact idea... no clue if something similar has been proposed previously, though. Could be an ego, too, but the effect is a little too niche to recommend that. The actual artifact type is fairly irrelevant other than being non-weapon... probably make it either whatever has the least current artifacts, or whatever doesn't have artifacts of its type that has race specific effects.
"Foo of the Chameleon"
<Appropriate stats for item type, if it has armor or defense, probably at least mat level 3>
+Cunning, +Defense, +Stealth
Reduces adjacent enemy's confusion resistance (possibly make an active instead of passive, using whatever an appropriate talent would be)
Treats player as any
race/class combination in regards to activating race et al specific artifact effects and talents.
And that's about it. Something that would treat the player as a demon, as undead, as halfling, as dwarf, as etc., etc., etc. all at the same time. Probably set up so they only get beneficial effects, but... maybe not, as well. No clue how the yeek-fur robe would react to you being both a halfling and a yeek at the same time, though