Still had no chance to try this :C
But I realized that the warmup weapons are chosen randomly and I don't think I have the chance to check whether or not the decoy weapon is a decoy.
SO I would either have to set HP to 1 for every round (even non-decoy warmups) or give up and not use this :C
The plugin (in my previous post) should check if the user has a decoy and if so sets health to 1 hp...