I think that feature should be added to the printerdriver and not to the underlying device.
I would certainly welcome any improvement to the printerdriver but I suspect that in this case it would also require a change to printer.device. I think it's printer.device that sends the final formfeed which causes my Photosmart printer to think a new print job has started. printer.device would need to be changed to send a termination code (that it would read from the printer driver) after the final formfeed.
My request here was not about changing the printer driver or device; it is to get the usbprinter.device includes added to the SDK so programmers can access the usbprinter.device directly just as they have been able to access the parallel.device with OS4 and classic Amigas. Some sophisticated programs like Pagestream have their own printer drivers and bypass printer.device by sending directly to the port device that the printer is connected to.