AC500 I/O redundancy

Hello guys, I have a question about AC500 High Availability system. I know that it is possible to make redundancy on CPU level. So I can take 2 CPUs and for IO system I take CI590 module (with I/O modules on the right side) connected to both CPUs. Everything is clear. But is it possible to make also redundancy on I/O level as with AC800M? I think that not but I need to be sure because our customer wants the full redundancy (CPUs and IOs) so the discussion will be mainly about the cost because it will be different price with AC800M. Thanks for the answer. Have a nice day.