Hi
Sounds good, but i did not found any online documentation.
Regarding your statement, that none of the existing libs meets your needs, I would say, that m2tklib fullfills almost all of your requirements. Additionally m2tklib support less than 4 buttons but also more than 5 buttons, rotary encoder, input and output from Arduino serial monitor etc..
I have added your lib to my personal lib of Arduino Menu Libs:
Library Name: LCDMenu2
Download: http://arduino.cc/forum/index.php/topic,73816.0.html
Library Name: LCDMenu
Download: http://arduino.cc/forum/index.php/topic,96104.0.html
Library Name: MenuBackend
Download: http://wiring.uniandes.edu.co/source/trunk/wiring/firmware/libraries/MenuBackend/
Library Name: LCDMenu
Download: http://www.metalgecko.com/arduino/LCDMenu.zip (does not exist any more)
Library Name: Arduino_LCD_Menu
Download: GitHub - DavidAndrews/Arduino_LCD_Menu: This library creates menu systems primarily useful for 16x2 or 16x4 LCD displays.
Library Name: MENWIZ
Download: GitHub - brunialti/MENWIZ: ARDUINO LCD menu library: short user code to manage complex menu structures
Library Name: phi_prompt
Download: Phi_prompt | LiuDr Electronic Solutions LLC Official Blog
Library Name: MenuSample
Download: Arduino WiFly Driver - Browse /MenuSample at SourceForge.net
Library Name: M2tklib
Download: Google Code Archive - Long-term storage for Google Code Project Hosting.
Library Name: OpenMoCo Menu Manager
Download: http://arduino.cc/forum/index.php/topic,131614.0.html, Dynamic Perception
Oliver