Depends if he needs something just a little softer or a lot softer.
For just a little softer he can hybrid with a multi like AlphaGut2000. I don't notice a whole lot of dropoff in spin with my ALU when I hybrid it with the AlphaGut.
Something like Fluoro or Black Widow will also give a little help.
For more softness, I'd go to Gut/poly next. Definitely more power and similar if not more spin. He'd have to take a bit to adjust to the higher power, but he might love it.
A soft multi would work great for the arm (as, of course, would all gut), but he might not like the lower spin.