Problematic shells are only a fraction of flying P3s. Maybe that's not as a big market for a company to invest in as we're led to believe based on complaints. These things evolve fast too, probably will be P5 time when someone can do it successfully as well... But the real trick is to do it right, just look at it that's really tricky to get the exact tolerances, angles and intricacies of the shell, I've tried myself to mold it and I'm quite used to doing these things, no luck this time tough, it's really complex and precise thus very very hard to get right. Not worth it IMO.
I've fixed/improved a few P3 shells here for friends using carbon fiber cloth and resin, it's a quick, cheap, easy and definitive fix. But it's on the original shell, a new one is quite a tough task. Also had a hard time fixing -actually rebuilding entirely - the screw anchors inside my P3P control, they broke after taking a few bumps in the trunk of my motorcycle during a marathon filming here some time ago. Being more careful now...