This has been a very interesting thread to read. Usually paint defects like blisters and bubbling are because something was on the surface that got painted over, and that's causing the paint to not adhere in that particular spot. Often it's oils of some kind, even the skin oils of someone touching the surface before it was painted.
Since the body panels are essentially fabricated plastic, I wonder if there's something IN the material that over time is making it's way to the surface (under the paint) and causing the blister? Like maybe it wasn't cured long enough, and a gas or something in the material is causing this?
This wouldn't be something Lotus did, or even an issue with the paint or their paint system. This would be an issue that came with the parts when Lotus got them, and they wouldn't have any way of knowing this until the problem showed up. This has to be frustrating for Lotus too, as this kind of warranty issue pretty much wipes out whatever profit they made from selling the car.
Like others have said, I feel bad for those that are experiencing this, as it's certainly not what anybody (including Lotus) wants.