Sounds like loose tenons would be the way to go. With ten
chairs the time used to make fixtures to hold the parts for
mortising would be worth while.

Though the jig shown at the following url is for a horizontal
mortising machine, it may give you some ideas for your jigs.
http://home.comcast.net/~charliebcz/.../RaysJIG1.html
check out the third page to see it set up for a curved chair
leg.

charlie b