Hi,
When you are supporting 2 players on mac, pc, linux, gamestick, ouya and beyond, you quickly see that the inputmanager is pathetic and ill-contrived.
What we need are Input Manager SETS, which can be chosen via build settings, so you have a set for ouya, a set for gamestick, a set that can be shared on desktop and so on.
This makes things pretty good to handle as opposed to a monolithic mess that won’t fit and won’t remotely handle 2 player for me. I can’t avoid using input manager because in a lot of cases its the only thing available to use.
I think what I’ll do is make a small component to swap input manager files and hope unity reloads them each time I do 
To be honest the Input Manager has so many other limitations that I’d never bother using it directly anyway. Having a different keymap for each platform is exactly what I’m doing in the layer I’ve built on top of Unity’s Input Manager.
Even then this gets a bit tricky what with all the unique inputs. I think this is a feature of Unity that needs a big old overhaul in light of the platforms it now supports. The Input manager was designed in a time when Unity really didn’t support this many platforms so it makes sense that it’s flagged for overhaul.