I'm not really familiar with the vim code base. From the little I've seen I'm astonished that people are actually willing to voluntarily work on it.
Having said that, googling revealed a bug report[1] where one of the main neovim developers states he would rather avoid "messing with a very obscure part of the C code." So yes, it seems to be difficult to implement into the existing code base.
There exists a plugin which adds some features, but because it is not supported by the editor core (hence the above emphasis on "native") it isn't properly integrated with other plugins etc.