2 things which I think would make a huge difference are:
1) Materials. Maybe if there was a way to have materials grouped by block it would make it a lot easier to see which materials belongs to which block. Currently I think it's awkward to have to do this by sight alone. The colofull image below is just an example, but hopefully you get what I mean.
2) Views. Maybe even just having a Left and Top view would help A LOT with positioning blocks rather than having to constantly rotate the camera to get the right angle which can be annoying. (Unless if I'm just doing it wrong)
3) UV's. Don't even get me started on UV's. This is basically non-existant. Want to export to Blender? Good luck.
These are the first 3 things that come to mind.