Actually thinking about this some more I think I'm aware of 4 solutions people have proposed roughly characterized as:
1 - Korean MMO style: NQ item synthed with % chance to break -> +1 synthed with % chance to break -> +2 ...
2 - Alternate take on 1: multiple NQ => +1.
3 - +1 mats = +1 finished product; HQ mats need to be rare.
4 - Some items require rare mats and can't be spammed for HQ; leave the rest as they are.

I think in different ways all three of them, at their root, are attempting to:
A - Limit the impact on the market of flooding NQs to obtain HQs.
B - Maintain HQ gear position as being "better than the norm" instead of "Oh, everyone has HQ everything".
C - Potentially also address the "gear never leaves the economy" issue.

I don't know all the ramifications of each approach but I think what I like best is a take on #3/#4 where you also make gear attune when durability drops below 100% the first time.

This would solve the gear never leaves the economy problem (it leaves as soon as someone uses it), maintains HQ as being not the norm due to rarity of HQ materials, throwing in #4 you get some gear that just doesn't HQ often because the HQ mat drops really rarely.

It also limits the amount of time I need to sit there as a crafter and spam synths to HQ junk components and prevents the disappointment of synthing all HQ mats and getting a NQ result.

On the down side it means that DoL need to spam harvesting to gather HQ mats and DoW need to spam NMs to obtain HQ mats. So, it's clearly not a perfect solution. I think I prefer it though. I haven't been able to fully think through all the ramifications though so maybe I'm missing a huge down side.