I think the way to do this is customizable Inscriptions (and insignia). Basically, you would craft a blank Inscription and pieces for each stat (one major, two minors), and then combine the pieces via the discovery pane. This would probably be more expensive than the normal Inscriptions, but not excessively so.
The advantage I see for this option is full customizability with a minimum of change from the existing system. No new major mechanics need to be created to make it happen, as it would just use the current crafting system. For simplicity, the crafting results would need to be account bound on acquire, similar to ascended gear.