Short Version: Anything wrong with running 6/3 NM in a joist well to a junction box that leads out to a 60A garage subpanel?
Longer Version: I'm thinking of finishing a room in my basement. It has a mess of wires that will need to be cleaned up and enclosed in the ceiling. This includes an 1.5" galvanized conduit with wires for my 60A detached garage subpanel. These wires could be secured between floor joists all the way from the main panel to just before the junction box inside the house leading to the garage. I'd like to remove that conduit (it's very in the way for finishing), ditch the old huge gauge individual wires, and replace that whole section with 6/3 NM-B stapled inside the joist well. Any issues with that? The current setup only has 3 wires from the main to the garage- I don't see any ground wire.
The first pic is the part of the conduit (and to the left across the basement) I'd like to replace with NM-B. The second is the junction box leading to the garage- in from the main on the left, down to the buried conduit on the bottom. The other smaller wires coming into the box would be removed. The third pic (actually 3 pics) follows the conduit back to the main. In 3a the conduit's not terribly in the way, but it would be nice to lose that (yet another) junction box that serves no purpose, and free up a little room in the utility room. In 3b is the place I really need the room- all those wires and pipes have to get pushed flush up against the joists and boxed in with wood to accommodate the low ceiling. 3c shows the main. The close part of that room will be finished, so all those wires need to be moved back into the joist well above the wall, as the arrows show.