The color coded version looks really good. – I think most of the existing icons could be changed to more simple, single color icons quite easily, if they are all available as vector files? Without the need for newly invented icons that should go relatively fast. The task should be best split up into chunks, so that multiple people can work on the icons at the same time. Reworking “only” a few hundred icons is also not as intimidating as changing all 1200 at once.
