You can use the same method to select a USART rather than an arduino HardwareSerial object, or add a 1284 to arduino ( which people have already done ).
The 'this->' is not useless in this situation, class declarations can be big, the 'this->' makes it obvious that the variable belongs to the class. People using the class for the first time will have an easier job modifying/understanding the class.
Anything that can remove a person from assuming something is beneficial.