Hello all. I'm wanting to build a gamepad that's 100% compatible to my Nvidia Shield (Android TV) and was wondering if either the I-Pac or KADE were able to be programmed for some of the advanced key sends. I want the Android Back and Home to be pushbuttons.
Welcome aboard, Agienne.

Just to clarify what you are trying to do/build:
1. Do you want to use arcade-style joysticks and buttons
or a handheld gamepad?
2. Are you looking for a gamepad-style firmware, a keyboard-style firmware, or a composite-device firmware that combines both? (Keyboard-style would probably be the easiest.)
Android Back and Home buttons sound like they might be good keypresses to add to the KADE options.
Degenatrons has made some requested KADE firmwares with custom keypresses and he also modded Android MK808 and MK908 TV Sticks for a project
here, you may want to drop him a PM.
If you're considering "rolling your own" by editing the keycodes, look at the KADE miniArcade source code
here.
"KADE/open software/firmwares/KADE miniArcade/sources/kade-mame-2p/mappings.c" looks like it would be relatively easy to edit the keycodes then compile your own custom firmware, but I've never tried it.

Scott