It exists now. Just use any other editing system... they all handle levels and color space conversions for you automatically.

There are standards for each format that you might deliver in. There is zero ambiguity about what the proper levels are. (Unlike other aspects such as whether or not you should account for the differences in the color primaries between Rec. 709 and SMPTE C and EBU. According to the standards maybe you should, in practice this never happens. It gets nasty if you were to do this... whenever you up/downconvert, you'd have to insert edit a new set of color bars onto the master. And of course it's nasty because a lot of equipment can't convert the colors.)