The most liberating aspect of writing Rhyming Slang was being able to smuggle two swear words past anyone reading it. Three, if you include "cream-crackered". In fact, now I read it again, I realise it's a veritable cuss-fest from end to end.
Rhyming slang permitted me to translate an otherwise straightforward retelling of the core story into something immediately flowery and melodramatic. It's a bit like polari or some other cant, in that it carries with it a flavour of cheekiness and, even fainter, not-quite-legality. If you translated each instance back through its derivation to the literal meaning, then... first of all it wouldn't rhyme (because a lot of rhyming slang is about obscuring the original rhyme), but also it would be pretty flat in comparison.
Concentrating on getting juicy slang phrases in there also meant I could avoid pantomiming the Cockney accent that it's usually delivered in. That was important because, as with a lot of other small differences among the original Queneauvist 99, it would be necessary to write an entirely separate Cockney exercise later.