I'm curious about the relationship between 尉-shaped characters and the pronunciation yu. I'm not sure if this is just a Sichuanese thing or not, but here's what I know:
In some Sichuanese topolects 蔚蓝(色) is read
It has been said that Deng Xiaoping often said: 芋问, which is really just: 慰问.
告慰 can also be read
gao yu, in some Sichuanese topolects.
蔚 can also be a surname that is read:
尉迟 is also a double barreled surname.
yu pronunciation seems like a bit of an anomaly and I'm not really sure how it fits in here. Perhaps it was that the surname was so strong in some areas that it affected the pronunciations of these other words.