The same way that inserters can be upgraded (yellow -> blue, blue -> green, blue -> stack), it would be great if cranes could also be upgraded in a similar way. As it stands, if you made a bunch of MK 01 cranes, and replace them with MK 02 cranes, there's nothing you can do about the old MK 01 cranes.

Alternatively, instead of the current recipe sets, simply let us combine 3 or 6 inserters into a crane of the same tier and also turn a crane back into the equivalent inserters.

I'll be considering changing the main recipe to include prerequisite cranes instead of inserters. On one hand the change will break a lot of people's mall productions but on the other i went to check my own finished pY save and there it was, a chest filled with 300 yellow cranes being wasted (so you're defo not wrong).