A few answers Letholas, thanks for asking!
We definitely think it is valuable to be able to adjust stats on some crafted gear - customization is one of the coolest aspects of crafting!
As far as recrafting changing those stats, the intent would be something like this would continue to be done through optional reagents, so in a case like that, yes, you could use recrafting to swap out those optional reagents and thus change the secondary stats.
The recrafting system described is very specific to crafted gear only.
The recrafting system shouldn’t be thought of as an upgrade system. It is just a way to take something that has been crafted in the past and recraft it with changed optional reagents and possibly a different quality. So to give a more concrete example using your numbers:
A crafted recipe might make a helm at between item level 325 and 335 depending on quality. It could require 100 dragonscales as it’s main reagent.
A skilled crafted might be able to make it straight up at quality 5, item level 335, while a new crafter might only make it at quality 1, or item level 325. In both cases, the reagent cost is the same.
Now, say you got your piece crafted by that unskilled crafter at quality 1 / item level 325. Maybe he’s a friend and says, hey Letholas, I’ve been working on my blacksmithing and I can now make that piece at quality 5! Send it to me via a recrafting order to me and I’ll hook you up. You do so.
Your friend then recrafts your helm using the old helm, 20 dragon scales, and one of a special reagent he earned, to recraft it. The result is it is now quality 5 and item level 335.
Hopefully that helps clarify.