Like yourself I find my ghillie brogues (bought in 1971!) to be far less than comfortable. A few years ago I was given a pair of the light-weight, synthetic soled, GBs made by Gaelic Themes. For what it's worth I find these to be very comfortable on the field, but don't know how they'd be for marching.

Generally speaking I don't wear GBs-- I prefer a well-made, and well-polished, oxford as these tend to offer better support and far more comfort. They are also easier to waltz in!