Certainly Lars can design a new Skat. A hull capable of cruising at 20-knots is very do-able. I happen to know someone who can help.
As for re-builds... the actual labor time is not all that long if you have a proficient mechanic. It could range from a few days to a couple of weeks. On the Millennium 140, a Pax-18 was pulled out and replaced in 2 days, in order to make it to the Ft. Lauderdale Boat Show last year. By the way... that motor didn't come out in one piece, nor did the new one go back in as one piece. Moral... throw enough money at something and you can create a time warp.
The real time will be consumed in sourcing the parts and machining the existing components. Add a multitude of other things that can go wrong in the dis-assembly and/or re-assembly... and the hours turn into days. It's not really the time these projects take... the real cost is in the time they take away from your business. That being said, hiring a good mechanic and chief engineer... is money well spent.