What's the minimum parts to swap if you want to go back and forth between XX1 and 2x10? Reason is that sometimes I like a tightly spaced cassette for lots of climbing (2x10), but sometimes want simplicity of 1x11.
These systems seem almost totally mutually exclusive - about the only possibility I see is common crank - i.e. m985 with wolftooth ring. Can rear der. or shifters be common?