Another thought that occurred to me late last night whilst lying in bed - screwdrivers. Really good quality Perfect pattern or London pattern cabinetmaker's screwdrivers. There are millions of plastic-handled things about, which are great for engineering work because the oil doesn't soak in but wipes off easily, but very few for fine woodwork. I think Crown and Joseph Marples offer round-handled, round-stemmed ones, but nobody does London pattern or Perfect pattern ones that I know of.
Maybe the range might include specialist screwdrivers for plane cap-iron screws and the like, saw-nuts (plain and split varieties) and maybe even gunsmith's turnscrews.
Not a big tooling cost, the forging, grinding and heat-treatment work fits with their existing expertise, as does handle-making. They already make some nice 'niche market' hand countersinks, scraper burnisher and the like, so the development from those would not be a huge step, and they have some market background to give an idea of viability.
