Re: UI must fully switch based on context.
"The problem is that you need a different design of application for touch and Keyboard/Mouse."
In Windows, yes. Chromebooks manage with a single interface rather well.
Last week I was asked by grandchildren to install a Lego application on a PC. It was over 400Mbytes. The problem was it had obviously been designed for an iPad and nothing at all had been done to make it PC-friendly. In fact it locked out everything else so when it needed BT access, it had to be closed completely to set up BT. It would have worked OK, I suspect, on Android but there didn't seem to be an Android version.
Lego is now permanently off my present list for being too lazy to produce a proper Windows version, but the sheer unusability with KBM was a bit of an eye opener.