How about an open-source resource site for kits and every available bit of after-market? Open-source so that anyone can log in and contribute. For instance; you want to buy a Sherman tank, but you don't know which to get - so all available Shermans are listed by manufacturer, and by scale, and a brief rating as to accuracy and buildability. Then a link to all available PE, resin, turned aluminum/brass, and 3D printed parts for that kit. Way too much work for one person, that's why open-source so that members can make additions or corrections. Make it for military kits as well as aircraft, ships, figures, cars, etc, to keep everyone happy.

https://www.scalemates.com/

Doh! But I envisaged a link from every kit for any relevant AM, instead of searching throughout the list, and finding by trial and error.

There is a link to AM parts on every kit page and vice-versa (Related products)... But maybe I'm missing your point?

See here for instance: https://www.scalemates.com/kits/1002597-takom-2047-king-tiger-pz-abt-505

Uhh, OK. That'll work. Who stole my idea??

It's probably my most used online modelling tool. A great site, indeed!

The developer is also open to new ideas if you have more