I wouldn't disagree that the K13 was possibly the best training glider of its era but doubt very much that it could be produced today at a sensible cost.
Back in the days of Pegasus Gliding Club at Gutersloh, a K13 became an insurance write off due to a ground incident. Damage was severe and included a broken main spar. Two club members bought the wreck, borrowed plans from Scleicher and, over months, rebuilt it. I recall they calculated that, after they had sold it, they had been working for something like 30p/hr.
The only job they didn't do themselves was the new mainspar which was built by an ex Scleicher employee who still had the jigs.