Quite frankly, I think the Android version just needs a new UI entirely. The buttons are entirely too small for a finger on 4 or 5 inch screens. There's been a few mockups in the old Android port thread.
I think the best place to start though would be if UI layouts and such were externalized. Then they could simply be handled by mods.
I'm playing on my 7' tablet and feeling comfortable. I think playing openXcom on phones won't be comfortable at all. In case of small screens you need to enlage buttons. Enlarging them you greatly reduce battlescape size.
Anyway my miserable attempts of at least changing background picture with buttons failed.
I wrote something like this but had no effect.
Maybe if I catch luck and get understanding with all this coding I think about 4'-5' version..