PG, I can't understand why you say "every board with a centreboard is a compromise" - or rather I can't see why a board with a centreboard is any more of a compromise than a board without one.
Sure, a centreboard adds weight; but so does adding width to a Formula board, or adding any length to a hypothetical board just 1 metre long. The centreboard basically allows you to vary the fin area, depth and angle whenever you want. It's like having a fin bigger than a FW fin, that's there when you want it and goes away when you don't want it.
Sure, it adds drag on a planing reach but it's faster in non planing or marginal planing conditions upwind and on a close reach.