Personally, I’m quite happy having two separate options - filmic already had too many options in it, IMO. (not complaining, just thinking aloud!)
I suppose it wouldn’t hurt sigmoid to have slightly more control in some way, thinking highlight gradation especially, but I’m not sure whether that is something that could be incorporated into it’s function in a sensible way.
I’m quite happy anyway 
BTW, in relation to the discussion further up this thread about highlight ‘clarity’ for want of a better word, I thought the image in the thread: Any way to recover the sky and highlights in this shot? - #15 by 123sg was quite a good example.