You can use a wider tang and get the same advantages for compression fretting. My understanding is that this is how Martin did it after they gave up...
Another issue will be that the thinner octave strings will sit down a bit compared to the bigger string which can make picking more difficult. A new...
I am mostly a bass player but bought an old flatback mandolin in an antique store several years ago. I enjoy playing it and have become more interested in mandolins.