Everyone say this with me:

"Gypsy, YOU'RE DONE FOR!!!!"

It'll be great at first, then you'll realize if you want to be sociable and play with other people in customary keys for various tunes, you have to learn to play them in second and third position up the fretboard to compensate for running out of high notes at the top (CGDA where's the friggin E string?) Nice addition to a session if you can pull it off.

Already have an octave mandolin you say? Well then the next thing you want will probably be a 10-string cittern--the hammer dulcimer mention is a dead giveaway that you are a multi-string tuning masochist...

there are many here among us...

I'd say more but I have to go tune something....

Willie-O