I halfway agree with the others. Make it retractable, but not spring-loaded. If you have to flip it out manually, that means you'll be paying more attention to where it's flipping. Also, you'll definitely want to make it out of plastic, sintra or whatever. I know the lure of wanting metal blades, as I originally had the same desire myself, but in most cons and many other types of events, any kind of metal weapon, whether sharp or not, has to be peace-bonded so that it cannot be drawn. They don't care if it does hold an edge, just that there is the possibility of it holding an edge. With a little Rub n Buff wax, you can make plastic look like metal, and pretty much any event security won't bother you about it.
Also, you may want to contact the artist, and the merc whose armor that picture represents. I forget who precisely, but they're both members of one of the South American clans. I'm sure they won't mind you basing your claw off of his, but it's still polite to ask. Aysin Fett is/was the original organizer of the South Americans, or at least of them getting into the Mercs, so she'll probably be able to point you at the right people.