As an amateur builder I don't think the weight target is the barrier to building, it's the how to meet the weight target that is the barrier.
John Kells Mayhem plans were really helpful, as were the now lost Steve Clark postings on the defunct US site.
There are many, many parts to an IC. Building one, or assembling one from parts will never be easy, but advice and possibly sharing molds not just for hulls but also for mundane parts like spreaders, carbon carriage rails, chainplates, cassettes, goosenecks, centerboard trunks etc can make a big difference. The tooling may be simple but when jigs and molds get shared so does the construction knowledge.
Every time I build a part I am constantly worrying about strength and weight. I like the challenge. It makes me develop simple, light solutions.
My boat, built from a Maas hull and foredeck, Maas carriage, Maas seat, Van Dusen mast, but Rawstron deck, stringers, boom, transom and fittings, will need corrector weight; semi-pro builds can meet the 50 kg minimum.
Are plywood hulls really cheaper and easier to build than carbon foam? It seems like both require molds and carbon. These boats will never be cheap to build from scratch, $3k for mast and sails, $2k of rigging, and the list goes on. Is saving $500 or $1k going to make a difference? I am not biased towards foam/carbon. I would gladly trade sawdust for blackdust and splinters for shards.