The function of eagle with automatic mirrors for coils is great and get 90% to what is needed for propper electrical drawings.
What is needed to supliment this is to have a cross referance placed on or next to components which are made of several symbols. ie a prtection relay is easier displayed with the input group and output group seperated but still refering to the same component without the need of a cross referance mirror.
This could be implimented very easily by placing the same referance place holder in the relevant position when designing the symbol/ components. A example is shown in below with the cross referancing done as described. Please note that this is not eagle but a dedicated electrical cad program
Further to this if the cross referance could be movable by the smash command this would make it eaven better