But my issue with the linked tool is that it does none of the things you mentioned. All it does it make already very easy things even easier. Is it really that much harder to remember `ffmpeg -i inputfile outputfile.ext` than `ff convert inputfile to ext`?
I've explained this in other replies here but I am neither saying that ffmpeg wrappers are automatically bad, nor that ffmpeg cannot be complicated. I am only saying that this specific tool does not really help much.