Customize the "Select input method" Dialog

Question

I think we all have seen in an Android device the "Select Input Method" dialog:

I have seen in several places different dialogs, customized for the different environments. For example, from the App Spanish for GO Keyboard:

I am fully aware that this does REQUIRE ROOT. That is ok, the App will only work in rooted devices.

So, I want to customize this popup (and also being able to select the displayed options). But I have absolutely no clue about how to do it. Can anyone give a hint about how I should proceed?? Thanks!

Answer 1

At the end the best solution was simple and didn't even require rooting: Create a custom keyboard with a 'KeyboardView' object and set this keyboard in the required way.