I do not understand well your question. You clearly describe an infrastructure but do not provide any details about it. You mention a new wan for guest. But you do not tell us whether guest exists in the current infrastructure or whether guest is entirely new. Am I correct in understanding that the existing infrastructure has a functioning wan and that you want to add a second wan which will be dedicated to guest traffic? If not correct then please provide clarification.
If we assume that there will be a vlan for users, with a separate vlan for guest, and assume one wan for users and a separate wan for guest, then I suggest that your solution might be to configure Policy Based Routing that will have a normal default route to send user traffic out its wan and will use PBR to send guest traffic out the wan for guest. One question about this would what you want to happen if one of the wan fails. Would you want all traffic to use the surviving wan? Or if guest wan fails do you want guest traffic to fail?
HTH
Rick
HTH
Rick
