We share some grief. When purely based on a "word" you're effectively picking a single character from a set of, what, 10^5? You say 7, after permutations? Either way, that original pool means a limiting factor.
I might be more pessimistic than you about the lifetime of a basic string like "mhallifwwas". It's not here yet, but it's the sort of AI, the sort of language indexing that's less like whimsy scifi and more like inevitable Big Data. Yes, I do expect tables to respond and evolve into phrase dictionaries.
In this context, nursery rhymes are shit. I like them to help illustrate the simplicity of use and apparent complexity gains. They're superstrong in the current meta. But once the new tables are built they'll wreck rhymes, pop song lyrics, quotes, sayings, etc. in a hurry. OTOH, the concept comes with implicit invitation to roll your own. Hell, they did it on Doctor Who. And I get the sense it's easier to add permutation to phrases.