A lot of hand wringing and worry over a simple front derailleur - don't over think it. Front derailleurs with flat cage plates are extremely versatile. An ancient Campagnolo Nuovo Record "racing" double derailleur from the seventies (pretty much the same design as in the sixties) will shift almost anything you can throw at it. It was standard equipment on my P-15 Paramount and had no problem with the 52-42-36 triple that also was also standard (other years of P-15s used 54-46-36 and 53-49-36, etc. with the same derailleur, note that these bikes used Shimano rear derailleurs) If the cage clears the chain stay, I have no doubt that it would shift a 44-34-24 triple today. The skeleton key derailleur that Riv is selling will probably work on anything that Riv sells with almost any crank setup as long as you don't get stupid with BB widths. There is always more travel than needed built into the the derailleurs - thus the existence of travel limiting screws. The stubby cage will clear the chain stays with compact cranks and low bottom brackets. The only thing that the stubby cage will not deal with is too great of a small-big chainwheel difference, but I have never actually had that problem with any derailleur on any bicycle. That said, I never use derailleurs that require adapters or shims any more, so it is unlikely that I would use one. Less parts = greater reliability. If it were available in 28.6 and 31.8 diameters and was all silver, then it would be another matter.
Time to get back to grinding/filing a small recess in the clamp of my NOS 31.8 Dura-Ace 7800 front derailleur to clear the water bottle mount reinforcement on my custom.
Laing
Delray Beach FL