I am watching this thread closely as I was considering the same raincoat question and was looking at Ventile. The olivey-green shades are also excellent. If you are a hard size to fit, you know the impossibility of finding a good raincoat RTW. Overkill or not, this is what bespoke is there for. I will say that some of the Italian silk raincoats tend to be easier to fit and also wear like a dream.
Re: ventile, the special instructions regarding stitching seem pretty crazy though, but not impossible.
Someone please chime in if you find a source for Ventile swatches. It looks great on paper, but I hope it's not too heavy-duty canvaslike. I have bad memories of armor-like bonded Mackintosh coats. The L24 looks good.