Using "Intelligent SNAT" for outbound traffic?

there are a couple of issues with that iRule

SERVER_CONNECTED won't be hit until there is a connection with the server, that connection needs to use the SNAT address you want so you should do this earlier, the CLIENT_ACCEPTED event is a good one.

then you do need to swap [IP::remote_addr] to [IP::local_addr] as that is the IP of the server you are connecting to (seems weird, but this is looking from the big-ip point of view)

i mocked something up that works fine on a forwarding IP or performance L4 virtual server

when CLIENT_ACCEPTED {
  if { [IP::addr [IP::local_addr] equals 30.30.30.30/24] } { 
    snat 10.10.20.50
  } elseif { [IP::addr [IP::local_addr] equals 40.40.40.40/32] } { 
    snat 10.10.10.20
  } else {
    snat none
  }
}

now it is up to you to add the classmatch stuff again if you need it. again if you get stuck post here.