I'd be inclined to go the threadless route myself - and I, too, own a top-end Puch frame/fork (531 all) which I've been building up/swapping out since 1982. I've thought of this scenario - bent fork - for some time. I, too, looked around for a replacement should that day arrive that my fork gets walloped.

I wouldn't worry about maintaining my Puch with vintage parts/components. It's the frame itself that defines these beauties. Threadless and top-end would be my decision.