I develop a lot of extensions for Fiddler. Some of them are public, others are private to my organization. Currently Fiddler4 is built against the .NET Framework 4.0. I don't want my extensions to depend on a different version of the .NET Framework than what Fiddler requires, which lowers the burden of distributing them. If Fiddler runs, then I can be sure my 4.0 extension will too.
It would be handy if Fiddler updated the .NET Framework version requirement. It would 1) give you guys more Framework to work with, and 2) allow me to up the framework requirement of my extension while still meeting the bare minimum that Fiddler itself requires.
There is a considerable amount of new cryptographic faculties in the .NET Framework 4.6.1 that would be handy for my uses.