Thx for the answers 
I suppose, the idea of this patterns is when we have implemented something, it would allow to use only the methods where T has its Traits, making more flexible code, so to keep everything organized is better to have several impl blocks and in each one set which are the needed traits for that group of functions.
We could actually use macros to make something like conditional traits.
@khimru Why do you say conditional traits is out of the generic's scope while there is the specialization feature?