Always pony imo... you can drown just the same in 10ft as you can 120ft. A spare mask isn't needed. More air than planned for, yes. Cutting devices x2, yes. Have you ever bobbled your trilobite in 5mm gloves? I have and I just grabbed my knife to clear the mono line and then picked up the cutter afterwards. Warm water diving is night and day different than sub 50° snowy water PNW diving. My solo dives in Hawaii still had a pony and 2 cutting devices (trilobite and bfk) but I had far better dexterity and less concern for loss of 1. I don't change my kit for different rec dives, I change my tank. 119 + pony for sub 60 fsw. 100 + pony for shallower dives. Now that I'm adding a dry suit I may just shelve the 100s since I can stay warm and dive longer.
At 9 dives this new diver should be looking at what he needs to be safe and a good buddy. A good buddy is fully self reliant. Being self reliant is the first step to being safe for solo. I don't think it's a great idea to go solo right now but I do think it's a perfect time for him to start gearing up for it.