would this be better as "Remove a +1/+1 counter from ~: Target creature can't attack or block this turn."? or would that be too good since it's repeatable? I mean as it is, it's kinda like a creature version of Change of Heart, so why not go ahead and make it a temporary Pacifism too?

I'm not sure I like having instant speed effects like this with windup. Lots of board complexity.

Also nonhybrid cards shouldn't be artifacts.

Second ability should probably have a tap cost itself. However, Alchemist's Vial was just printed doing something very close in colorless.

An interesting option is making it obligatory: "At the beginning of combat on each opponent's turn, remove a +1/+1 counter from ~. If a counter is removed this way, target creature can't attack this turn."

But that is rather wordy.

MOON-E : Windup at instant speed adds a lot of complexity already, yet the timing of this does not overlap windup's decision making, which makes it overall less complex. The defending player controlling Brass Emissary must declare if he uses the ability before attackers are declared, so before any commitment from the opponent. This is the equivalent of gideon's law keeper in other sets.

If we want to lower the wordiness of the card, why not just have it tap target creature? Effectively the same but without the headache of trying to remember why something can't attack or block for no obivous reason.

I second making it tap, but also am of the mind that these counter removal abilities are too complex in general.

if you feel the complexity of the counter removing is an issue, we could give it a tap ability like Gideon's Lawkeeper. Then there would be tension between winding it up and tapping something down.