Only downsides to that is you're using more coil, thus more inductance and also more mass, which makes the sub less efficient and requires more power. Other than that it's a good design and more linear than XBL^2. If they don't get too happy with it (going to the extremes of excursion and such) then it'll be fantastic.
depends on what xbl^2 motor.....parthenon? and i actually read on sounddomain.com that adire patented a motor very similar to the lmt motor, they called it the v12 something another 9er, they said they did it in the process of developing the xbl^2 motor.