I know you have this miners are happy with the 1MB limit mantra, but does past actions on behalf of the miners support this?

Miners used to limit blocks to 250kB, then 500kB, then 750kB, and then 1MB. That is, in the past they have implemented a soft limit in policy.h or using -blockmaxsize command line option. If they wanted to squeeze fees higher, they could reduce the block size now. They can't increase it as they have hit the protocol consensus limit.

For those that say BU not tested? It might have some bugs that need sorting out, but they do seem to have their own test chain: