|You should be able to cascade two or more switches together so they behave as a single unit. At least, I would hope Cisco is capable of doing this. I know the Avaya (was Nortel) switches we use do this quite nicely.|
My largest 'stack' at present is 5 switches, but you can cascade as many as 8 together at one time and have them behave as a single switch. I have the stacks setup with multiple uplinks that utilize LACP so should a single switch, or uplink fail, the rest of the switch still continues to work properly while you replace the bad switch.
I'm sure Cisco does this too, you'll just have to research it.
You will still have two single points of failure though once you make your switches redundant. Your single router and your single external connection.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.