Just a thought on toys and I am sure you have a lot of great ideas also. Of all the macaws I have dealt with severes seem more into being on ropes and balancing on them. When given the choice I have seen them choose going over a rope more than any other type of perch or play area. Crawlers or nets are wonderful and they would stay there all day and play. If not available I have used a boing with a twist to loosen the braid I then stuff food into the creases.
I have taken braided rope and strung it from one surface to another with toys wedged in.
Or send the bird to John....he would love Johns bird play area set up!!!! How do I know this...mine have their bags packed ready to visit John.
One more thought...training. When you have an animal that is great but are harder to manage as most people would manage them why not have the people learn some training skills. One breed of dog I have can be stubborn and the breeder requires at least a basic dog training course. For a species of bird that is known to require a higher level of training skills why not have them let you know what training they have had, do they know any training techniques and if not ask them to visit have them work and teach a parlor trick to the bird. There are some simple things that can be taught or learned in just 20 minutes. My mantra is "DO NOT TAKE THE BITE" and I really believe that. People need to know not to push, have patience and know how to encourage a bird towards behaviors that mesh with their environment.
Regarding severes...they are so cute, funny, clever, intelligent, have a mind of their own, get bored easily, love to play play play, are very food motivated and can be truly loving. Have someone that understands this about them and work with their wonderful traits...you then have a fantastic bird... I see them in some ways like a border collie...are great at performance sports. Not the type of animal you want going to a sedentary life style. They need a job and to be kept busy and I think this is where people go wrong getting severes....just like the high rate of border collies in rescue people don't understand them or their needs but in the right home are both fantastic animals.
Peggy