Personally my thought was to focus on buffing up their gunblade and to mix ranged and melee attacks together. I figure a combo-less, no-positional melee class would be best. Maybe make their damage be based on distance rather than angle if there's going to be any positional stuff.

I've been working on my own interpretation of it, using a mixture of Samurai's Kenki Gauge, Machinist's Ammunition, and the elements from Black Mage to give it a melee magic DPS feel, with DEX as its primary stat.