Alot of the screen drivers use specific resistance sensing to know what button you are pressing. The driver boards that come from 4layer do not need relocated resistors as the daughterboard is only tacts. The resistors are mobo side. So all you need to do to activate those button presses is ground that specific pad. Press menu? Connect menu pad to ground etc etc... That can be through a tact or some sort of transistor switch setup.
@CrazyGadget sells amazing little screen control boards that are controlled with the d-pad and face/shoulder buttons. Or if you want to install tacts on your custom you can go that route.
For a board like we use for gwii there is only one control input pad and each tact has a specific resistance value between ground, itself and the key input.