Hope to see this in the future update.

We can farm from the 3D world for the ingredient to combined with another gem from weapon smith at the street.
Make it simple like following:

Diamond Gem (as reare as the relic): lootable from world, of course tradeable and auctionable
+
Upgrader Gem: purchase from weapon smith with Plat (for plat weapon, firebrand, immortalius) or Gold (for Gold weapon, Nightshadow, serrated axe & infused hammer)
My suggestion price for Plat :50plat And gold: 1milion Gold respectively

= udgrade the weapon to your current level.

Example:
You need
1 Diamond Gem + Upgrader Gem (50plats) = upgrade firebrand (level26) to firebrand (level31)

Or

1 diamond Gem + Upgrader Gem (1 mil Gold) = upgrade serrated Wing Axe (level31) to level (36)

Common STS.
Make all this weapon worth for something
I don't want to keep my Level26 firebrand in the Stash to collect dust.
With implement the above, definitely will Help u generate plat income & also sink the Gold.

Any thought guys?