Connecting HID controller as keybord I'm about to buy an HID controller(Green Throttle Atlas Single Controller, w/ upd. firmware) and I've heard a lot that most of the games on Android do not support HID controllers, but they do keyboards.
I was wondering if I will be able to remap controller as keyboard layout; that is, make Android see keyboard connected instead of HID controller. Preferably without root. I'm on Nexus 5.
I have a nexus 5. It works fine, havent had an issue with any games so far (that is including play store games and emulators/roms). Once they pair through bluetooth, you can map the keys to what ever you want (in emulators, not play store games). 

the only issue i have (and i think you are talking about) is with it working on a computer. the current HID controller driver that it uses seems incompatible with PCs unless updated. i am currently trying to find the correct drivers for it to install but according to what others are saying, ever since google bought green throttle, the firmware+drivers have been removed everywhere.