Both lcd libraries determine RW pin (for example 12). If lcd used for writing only, can be pin 12 used as an extra I/O?
By default, the LCD4bit library does not use RW, but note this is defined as pin 11, pin 12 is used for the RS line.
I suggest you may want to try the latest LiquidCrystal library before writing too much code for the less capable LCD4bit library.