Mapleean

Hello, Would it be possible to have a boot loader on a mobile device that can still support the hidden partition function and go into 2 separate android OS installations? I can see a problem being there's no keypad etc for you to enter your decryption key. Would it be possible to develop a boot loader to a point where a keypad could come on screen? Or i was thinking maybe just an external keyboard/numpad connected via USB-C could be easier? If anyone reading if familiar with the ins and outs of Vera...