We need to add libinput support since distros already started preferring it to synaptics. But we also need to keep synaptics support intact for distros that rely on it.
I think the best is to use linuxmint/cinnamon-settings-daemon#131 as a reference implementation. Some backporting from gnome is needed before using that code though. We lack some code refactoring and cleanups and some features (like separate motion settings for touchpad).
This issue is split from mate-desktop/mate-control-center#133 to track only m-s-d changes.
Ok, #166 is merged, so it's done.