After some consideration, I’d like to give other thoughts about rhythmical editing/writing.
Dorico understands a rhythmical value as a whole, regardless of display decomposition; that’s the new paradigm. But Dorico’s writing options contradicts this new paradigm: only traditional musical values are available (16th, 8th, quarter…). For instance, in a 12/8 metric, a 5x8th-note long (doted quarter tied to a quarter) can’t be written at once, though Dorico will finally handle it that way. At the other hand, in a 12/8 metric, the best way entering a 4x8th-note long value (doted quarter tied to an 8th) is by entering a minim; however, entering a minim in this case doesn’t really makes sense (musically speaking). Those two examples seem a bit contradictory to me. If Dorico would go to the end of it’s new paradigm, entering values should be something like entering a 3x8th, 4x8th or 5x4th value (instead of traditional values), though it would probably not be the most intuitive way to go.
I think the actual “hybrid” model should be kept but with the possibility to lengthen the value with fewer steps; for instance, a single key that would automatically “add an 8-th note” to the note being just edited (even a 4-note chord), or a variation on the R (repeat) function that would add the rhythmical value selected.