I'm sad nobody has at least given some encouragement yet.
On your diagram, you have the on/off switches for all 3 elements breaking the SSR's control circuit. If one of your ssr's fails closed it'll leave your element powered up. You've got an e-stop, but I would recommend moving those switches to a/the (depending on the element) hot leg between the SSR and element. Also, I'd use the switch to control a mechanical relay that actually closes the element circuit. It keeps you fomr switching the full load power (you can use a smaller control current/voltage to operate the relay, just in case).
One other comment, you don't have any circuit protection in there. You should add appropriately sized fusing or breakers. It's really not 100% necessary, so long as you use wires, switches and lights capable of carrying the full current, but wiring that thing up with 8ga throughout will be a bear. If you throw some fuses in there you'll be able to use much lighter ga wire to power the pid's, power supplies, and basically everythign but the elements. Makes for a cleaner and less frustrating job.
If you want check this out. I'm not saying that you should follow it, but it shows how I wired up my panel.
The power to tax, once conceded, has no limits; it contains until it destroys. I was not joking when I told them to dig into their own pouches. It may not be possible to do away with government sometimes I think that government is an inescapable disease of human beings. But it may be possible to keep it small and starved and inoffensive and can you think of a better way than by requiring the governors themselves to pay the costs of their antisocial hobby?
R. A. Heinlein