Of course you can. You can mess with any of the signal pins as much as you like.
It's only on the falling edge of the Enable pin that the state of all other pins are latched to the LCD.
Hence you can connect multiple LCD modules to all the same pins, but they each need their own Enable pin.

What I think will happen if you set your own state for RS and then send a command with LCDOUT,
is PBP will change straight back to what it wants.