On GMG's: No. Never again. I wasn't even there for that incident and I know how bad it would be if that was back on the map.
On reducing the number of traders: I like this idea. Roaming traders should still be around but maybe only two or three of them per restart, plus the static traders. The fact that there's still a safe-zone at Limni Fish Market means that you can still perform (relatively) risk-free trades. PvP is a part of Arma and it comes at times when you want it or not.
On reducing the number of choppers: All about this. 70/243 vehicles on the map being helicopters is pretty big, but I've only ever seen one group on this server use them efficiently as killing machines. Flying a chopper is always a risk with the AI patrols (fifty caliber road convoys and flying miniguns) and players such as myself that like to use them for target practice. That said, a number as low as thirty or forty choppers should be plenty and actually make treated as rare as they should be.
Pricing: The fact that my chopper only sells back for about 2k makes it worth the risk of putting on my roof to store it. The fact that buying at the custom traders can sometimes cause a spontaneous explosion and loss of funds when the choppers appear inside trees or buildings. Vehicle pricing is already low and doesn't really need adjusting, in my opinion. Maybe increase the price on the HMG vehicles, that would be fine.
Farming vehicles to make money is a slow and steady income, I'd say. You're still at risk while you're doing this, just as much as doing a Gold Haul mission or Home Depot because it takes hours as compared to minutes.
However, I'm curious what everyone's thoughts are on the number of vehicles on the map. I'd be fine with 150 per restart. Just my opinion.