I think the reason many wives go onto cuckolding their husband is because they no longer satisfy them sexually, but don’t want an affair.
So, to encourage a wife to cuckold you, you need to use toys on her to allow her to have great orgasms. This will encourage her to look for even better orgasms, which will eventually lead to her going with other guys.
Being caged is something that happens after being cuckolded, so I wouldn’t start with that.