It's close to what I've been planning for my fighter's next life. I'd been thinking Dwarf 18/2 with WSS for faster ki gen and khopeshes for bosses since the fists will be such low dice and crit range and I'll have khopeshes already crafted.
Others may scoff at the choice of past life but I think +1 to hit and +1 to stuns is going to be very useful with U9's increased saves and helpless changes.
As for getting nerfed, who knows? While that's certainly a possibility, I don't see anything overpowered about a Kensei being good at stunning since their strength is supposed to be tactics anyway. I've always wanted to get some use out of that ki gen bonus Kensei gives and maybe I'll get a chance for at least an update or two.
There are certainly a lot of trade-offs (monk DR/AC/damage/HP/saves/imp evasion/stances and finishers/abundant step/etc...) that are made to buy the stuns and the value of stunning is somewhat diminished in U9 anyway. The character will not be overpowered as a soloer, but should be a nice complement to well balanced groups - something I'd hope Turbine encourages.