Some airplanes have a surprising amount of "growth margin" built in; others can often handle such growth with minimal modification. However I suspect the RV-12 (and most other purpose-designed LSAs that meet the regs without winks and nods) can't do this.
The current LSA rules have fixed weight and performance limits; given how many people already see these airplanes as "payload challenged" most designers will likely optimize the airframe to maximize payload while still meeting the necessary structural margins. Doing otherwise adds structural weight for no advantage (see the fixed weight limits).
If this improvement goes through (I'm optimistic about the contents, if not the timeline), then assuming nothing in the current product line fits, I'd expect Van's to come out with something compliant to the new rules. But, I don't work there; I'm just speculating like everyone else.
- finishing kit and systems installation
There are two kinds of fool in the world. The first says "this is old, and therefore good"; the second says "this is new, and therefore better".