The 1410 should suit his needs as it will be a bit longer rotor and maybe 200-250kv less than he currently has. If not, this motor on 3s should be killer for the 9E. Considering people run the Tekin 1700kv on 4s buggies with no issue I don't see the problem with running a ~3300kv motor on 2s for the 9E but it will be on the slower side. Also it will be availible in mass quantity, easily rebuildable once their repair kits come out, won't take weeks to construct, and will be considerably cheaper.
Don't get me wrong the true Steve Neu motors are great but when it comes to convenience and practicality the CC/Neu versions liscenced by Castle are superior for the mass market IMO.