Our company did a project with SSR's once to sequentially power up several pieces of equipment. We used SSR's for the different groups, but did fit a heavy master relay which cut off the mains completely if all SSR's were off. That way you get the best of both worlds.
Remember that an unloaded SSR switched mains outlet is unsafe, even when the SSR is switched off. The relay gave the security that when the seuencer was off, the outlets were physically disconnected from mains.