The weight of the driver is not really a factor so much as a side effect of the engineering. You want to look at it in terms of total volume displaced and the sensitivity (if you are thinking about efficiency). Drivers with more surface area & excursion typically do have larger magnets and support structures.
LFE reproduction is all about moving large volumes of air by any means necessary. There are relatively featherweight subwoofers that literally use fans to move volumes of air and achieve performance that is impossible in traditional drivers of any weight class.
Doesn't really matter how you do it as long as things stay in phase.
