While the water pump that Subaru installed in the Justy seems quite adequate, It can be a real bear to service if it fails. People often damage the seal when installing the new pump, especially if they attempt an in chassis repair.
If someone wanted to it would not be too difficult to replace the mechanically driven factory pump with one that is separate and electrically driven.
It would require the removal of the impeller from the engine's front cover and blocking off the hole left by the drive shaft of the pump, with epoxy.
Then it is a simple matter of using a pump similar to this one found on this link: