Customize On touch keyboard windows 10 (using Keyboard layout manager or else)

I'm currently working on a web application with a touchscreen UI. The client is asking about a custom keyboard, I have tried implementing a custom keyboard with html/css but the result was not satisfying (behaviour not always optimal). Then, I found the keyboard layout manager, but it seems like you're not allowed to remove certains controls (windows caps, smiley,...) and customizing the color did not work as well.

I was wondering if there was any other ways to customize the onscreen keyboard from windows 10 (mainly adding/removing controls, and changing the color)? Or a way to have a touchscreen keyboard behave like the one from windows 10?

Thanks in advance,

Lionel