I think RNG stat mods are a bad idea for a full a full loot pvp game. It works very well in themepark mmo, because you never lose any items and it's one of the main goals to improve your gear, spending days/months to increase stats just by 1%, falling in love with it.

I'd prefer a more controlled way to manufacture T5 loot.
Inspired by reverse engineering, here's how the manufacturing process would work:

Let's call this feature Organic Morphing
The combination process would require a T4 mod and the newly discovered Niani Organic Enhancer(NOE). NOE's can be acquired from high ranked NPCs, SAP and artifacts, Syndicate shop(?) and are ranging from level 1-10.

You now put your T4 mod and NOE of your choice and start the morphing process. Due to the nature of organic matter, there's a chance for the NOE to reject the module thus destroying both items.

If successful, the newly created item will be T4.1 - T5.0 tiered, depending on what level NOE you use.

When you finish an assignment, the only location you can teleport back is the main terminal, regardless of where you accepted the assignment. This discourages accepting missions at field terminals, as you have to run back to them manually.

My suggestion is to add the field terminal from which you accepted your last mission as additional teleport location. I think this will make running assignments on field terminals more efficient and thus encourage people to spread out more, which is not the case right now as seen on the recent heatmaps.

Example:
1. Accept mission at field terminal SHI-18 on Shinjalar
2. Finish mission
3. You may now choose to teleport back to the main terminal or field terminal SHI-18.