Interesting effect. With the second ability, I want to ask you how you think deathtouch and normal damage work with creatures with negative toughness. For the third ability, I really don't trust state triggers that involve sacrifice or destruction; what happens when you get an Assault Suit? (The game becomes a draw.) I recommend the template:

"Damage is dealt to creatures you control in the form of -1/-1 counters.

Creatures you control aren't put into the graveyard for having toughness 0 or less.

Whenever a creature you control has power 0 or less, put it into its owner's graveyard."

RE: dude1818 "deathtouch and normal damage with negative toughness"

107.1b ... You can't choose a negative number, deal negative damage... However, it's possible for a game value, such as a creature's power, to be less than zero. If a calculation or comparison needs to use a negative value, it does so. If a calculation that would determine the result of an effect yields a negative number, zero is used instead, unless that effect sets... a creature's power or toughness to a specific value, or otherwise modifies a creature's power or toughness.

Deathtouch and normal damage should be covered in the first ability and should behave in essentially the same manner as a creature with wither would in the same scenario (i.e. wither + deathtouch, wither alone, respectively). For example, a blocking creature with deathtouch creature would still need to deal at least one point of damage (converted to the form of -1/-1 counter, its still damage) to apply deathtouch. The attacking creature would die from the effect of deathtouch since this enchantment does not save it. Normal damage would just put a number of -1/-1 counters on the attacking creature when damage is calculated and dealt.

See: 702.2b Any nonzero amount of combat damage assigned to a creature by a source with deathtouch is considered to be lethal damage.

Otherwise, I think that is a good revision to the card template and I'll talk with the other people working on this set about it.

You'd think so, but if you actually look at the state-based actions, "704.5h If a creature has toughness greater than 0, and it’s been dealt damage by a source with deathtouch since the last time state-based actions were checked, that creature is destroyed. Regeneration can replace this event." (Emphasis mine.)

Oh, and I was thinking of the corner case where you cast this when one of your creatures already has damage marked on it

Heh. Well, perhaps this card can be assumed to come with a tweak to 704.5h to remove the "toughness greater than 0" clause :)

But what else does that break? (I honestly don't know, but I figure it's there for a reason.)

Couldn't you effectively get the same by using "Switch the power and toughness of each creature [you control]." and "Each creature [you control] assigns combat damage equal to its toughness rather than its power."?

Having both of those on the same card is very confusing.