Hmm, like the idea. Comment: this is like the susalian chainweave agument (can't remember what book), a suit of chain shirt or chainmail of this grants DR 3/piercing, for an insane price (16,000-32,000 I think). Now, Definitly should not be making metal armors out of this, just. no. I would say non metal armors such as padded, leather, studded leather, hide, and any other similar armors in your game. Really though, if you inted a thick suit of this to be armor, it needs to be it's own armor type, not a modified suit of another armor. If it tightens and blocks blows when struck, it's going to hamper movement a bit. Here's my idea:
Stahltuch suit: +2 AC, +6 max dex, 0 check penalty, 5% spell failure, wearer gains DR 2/piercing. Cost: somewhere around 10,000gp, costs 2,000gp more to enchant (just like cold iron and weapons).
Stahltuch Bundling: +4 AC, +3 max dex, -2 check penalty, 20% spell failure grants DR 3/piercing, costs 25,000gp, enchantments costs +5,000gp

I completely made those up on the spot, so take em' with a grain of salt.
Unfortunatly, I have issues with most of your interperetation: the movement penalty is because the armor is medium/heavy, so what you want is a reduction in armor category, and that should be no more than 1 (full plate restricts movement, period). Spell failure should not be removed, only lowered, materials which have done this are mitril (-10%), and some thing in races of the wild (-5%, works with more types of armor). Max dex bonus applies even to padded armor, all armors have a max dex bonus, period (anything thick enough to protect you is going to hinder you IMO). Weight remains the same: so 50lbs of cloth full plate isnt going to interfere with movement? And finally: enhancment cost: would be a great balancing factor, except it costs too much.

Hmm, trying to be constructive...
I think what you want is like mitril on crack, so how about this?:
Stahltuch: any armor can be enhanced with stahltuch, replacing relative amounts of normal materials. padded, leather, and studded leather are replaced completely, all other armors are enhanced with thick layers of the cloth, replacing some parts of the armor, and thinning others. Armor enhanced with stahltuch is considered one step lighter (heavy to medium, medium to light, light to light), has it's max dex bonus increased by 3, it's armor check penalty halved, rounded down, min 1 for medium armors, has it's spell failure chance reduced by 15%, and has it's weight reduced to 1/3 normal. Cost +2,000 light, +7,000 med, +12,000 heavy, and an additional 2,000 for magic enhancement, as the material resists magic. Combining Stahltuch with mithril increases it's max dex bonus by +1 (to a total of +4), allows med armor to have no check penalty, reduces spell failure by another 5% (total -20%), and reduces the weight to 1/4 normal. Using mithril with Stahtuch costs 2,500 light, 8,000 med, and 15,000 for heavy.
Wheee, also completly on the fly.
Just my thoughts, take em or leave em.