Hey Matteo,
My experience with playing Nomic?
Each game is different. Sometimes a game grinds to a halt pretty quickly, others seem to go on forever, many are somewhere in between those extremes. All are interesting in their own way.
Which ´type´ a particular game of Nomic turns out to be depends, in my experience, almost 100% on the players of that particular game: their individual personalities and attitudes, and the group dynamics.
And that is, for me at least, the interesting part... how people behave in a Nomic game context tells you a lot about who they are, what they value, why they act like they act in real life.
That said, not sure Nomic is the type of game you would want to run in a workshop setting at a client. It´s hard to time-manage and can get somewhat ´ugly´.
I didn´t know about Blank. The basic idea is indeed the same as far as I can see, but Blank seems to provide some meta-rules in order to make it more manageble/playable.