“Would it be hard to make the vertex snap work in the blueprint editor, since positioning components in the blueprint editor is a pain.”
Yes that would be quite a challenge since the code for blueprint editor viewport is on the Editor side.
I implemented my Vertex Snap editor by creating my own editor mode for the level viewport, a functionality and method that Epic encouraged and has provided a code path for.
Modifying the existing code of the blueprint editor viewport to receive new keyboard and mouse inputs would probably be hard to do without a custom engine build, which then prevents me from offering the vertex snap as a plugin.
It’s quite doable of course, question is whether it can be without requiring a custom engine build 
If I get and find anyway to modify the blueprint editor viewport code in a plugin fashion I’ll let you know!
I am glad you are enjoying my Victory plugin!
PS:
My Latest Node Release ~ Get Distance Between Two Collision Surfaces!