The Jeweler's Tool Kit is a neat, if moderately expensive, limited use item. I'm not sure I'd ever buy them, but you never know. I think I would consider it more if they had more functionality.
I got to thinking about augment slots and I realized that there might be many items out there with guild slots that people wished had the new augment slots and that there may be some who like their old guild slot items, but wish they could get them on the newer drops. There might also be those who wish that they had a different color slot on their newer slotted gear. They killed new drops of guild slot items, but the code is still there, so we could conceivably craft our own if they let us.
What if they made it so that the Jeweler's Tool Kit was able to change the size/color of a slot and also allowed conversion from colored to guild slot? I haven't done a serious comparison of value of size/color vs TP's spent on uses of the kits, and any final cost would be up to Turbine, but it could look something like this:
Upgrade Tiny Guild Slot to Small Guild Slot = 1 tool
Upgrade Small Guild Slot to Medium Guild Slot = 1 tool
Upgrade Medium Guild Slot to Large Guild Slot = 1 tool
Change a Large Guild Augment Slot into a Colorless Augment Slot or vice-versa = 2 tools*
Change a Colorless Slot into a Yellow, Blue or Red Slot = 2 tools*
Change a Yellow, Blue or Red Slot into a Yellow, Blue or Red Slot = 1 tool*
Change a Yellow, Blue or Red Slot into a Green, Orange or Purple Slot = 2 tools*
*The slot would have to be empty in order to perform this work so if there is an augment slotted there goes another tool.
I suppose they could allow downgrading of guild slots to smaller sizes too, but I'm not sure if anyone would really do it.