I love blades from a space and cable management perspective but I really hate them for ESX. From a redundancy perspective, I would certainly agree that having (2) separate chassis installed in two separate racks with different power feeds and separate network uplinking to two or more uplink switches gives you higehr availability.
From a switch perspective and DMZ as one person indicated, you could dedicate (2) interconnects on one chassis to your inside and (2) other interconnects to a DMZ network if you wanted to separate at the physical layer. It would unfortunately only allow for (2) nics to be setup for failover and used for SC, vmotion and vm's. That said, you would still need to lose a lot for complete failure but you could still achieve server availability