software that i've worked on called Trinity Full SET Maker which can create full set in less than 1 - 2 mins and can also base the custom made items on an already made items by you or by default it just depends on the select.
Please it's very important to watch the video to understand how this tool works.
Details :

Create Items out of Best Tier / PVP items already in a blizzlike server.
Create Items out of an already made items ( unlimited amounts ).
Delete the items that has been made by the tool.
Create Vendors for the items and list them ( SET - Off Set - Weapons - Accessories ).
Delete Vendors.
This also can be used with the MultiVendor Script.
Add your prefered Custom ExtendedCost.