Technically you could. As Rob said, you still need a service OCPD(s) and it must be "immediately adjacent thereto". So you could have, say, an 800 amp NF disco, and that feeding (4) 200A fused discos, but why would you want to do that? You could have the 4 fused discos and just get rid of the NF disco. The only reason I can think of is to use double throw switch for say a generator connection. What are you trying to accomplish?