> Optimistically, middlemen or automated tools that ease the pain of changing in hard-to-enter markets.

Not sure what it's like outside of the EU, but what made it easy and attractive to swich mobile operators here were neither "middlemen or automated tools". It was regulation. Namely, the EU directive that forced mobile operators to allow you to take your phone number with you when switching to another operator. Before this you had to get a new phone number when you switched operators, which was a huge disincentive.