Those pleating possibilities look great, but not being a kilt maker, I couldn't offer any insight into their feasibility.

I will say though, that I would keep the sett large, and go with pleating to alternating pivots. I have an 8 yard kilt in what I call the "Ross Hunting 2.0" tartan, which has an extremely large sett (about 8 inches to the HALF repeat). It is pleated to alternating pivots, and looks great. The same can be done with a 4 yard box pleated kilt, so either way, you'd likely be fine (so far as a non-kiltmaker can tell).