Adding multiple Dye channels and the ability to dye any piece of gear really depends on how they've laid out the existing system. If it were done well (which I'd HOPE it was since they implemented dyeing in the first place, but I doubt it was considering everything else about this game's development), then it should be a matter of design discussion. The technical changes should ideally be fairly minor, and it would come down to the art department to decide which channels they want to specify for each piece of gear and then taking the time needed to mask or map those.

Un-gendering gear sets would be a nightmare though as trying to adjust the current models would be difficult and require a load of QA where it is even possible. Otherwise entirely new models would have to be added, so yeah, I don't see this one happening.

The log needs to happen though, difficult or not. It would likely involve breaking the item and its skin into separate components, a la GW2. In this way, you would unlock a skin rather than an item, and if multiple items share the same appearance, they would point at the same skin. This could also help to get away from the dyeable and non-dyeable gearset duplication, but they've baked that into crafting at this point, so there would be some cleanup needed there.