One thing I'd really like to see is something like the hammer face edit sheet. The current way to edit uvs is a bit annoying.
This would make precise texture alignment for tricky surfaces much easier. (Justify, texture scale in texels, and treat as one) Hammer also has it when you select a face, then alt + right click on another face you extend the uvs to that face. Even if it's not touching.
Forum post (https://forums.unrealengine.com/showthread.php?135144-Mesh-Tool-A-Mesh-Editor&p=740161&viewfull=1#post740161)