Sharing that pin will cause no problems (as long as you do not attempt to send data to the tape drive and to printer at the same time). Of course, you will also have to customize your software, or BIOS ROM, or the BIOS jump vectors in RAM, in order to take advantage of the modification.
=== 8bit Printer Port in KC Compact ==
The [[KC Compact]] uses the /EXP signal (Bit5 of [[8255|PPI]] Port B) as 8th printer bit. Amstrad CPCs can be rewired to do the same.
=== 8bit Printer Port in CPC Plus ===