What kind of series do you race in that generates 3 Gs sustained when cornering? Most good setups with street tires can't touch 1 G; with slicks i.e. Hoosiers on a production car, getting above 1.2 G would be incredible.
I still don't get how you say that all coilovers are bad. Companies like Zeal, Ohlins, Aragosta, Advance Design, etc make incredibly good coilover setups with very good damping, different spring rates, some have multiple damping adjustment and external reservoirs, etc. A spring and off the shelf shock could never compare to a setup with such adjustability.
Putting coilovers on a car could make it understeer; however, understeer is a characteristic of balance. If all the cars you've worked on understeer with coilovers, that just means the front rates are too high, rears are too low, or some combination of the two. MANY other factors contribute to handling balance, but these are a few that are directly related to spring/shock choice.
Man, I don't even know what to say. You can't go around telling people that coilovers are bad and that springs/shocks are the best setup because that is pure MISINFORMATION. There are so many different options in each category and uses for cars that you can't just say one is better than the other. However, coilovers are generally better for track use, autoX, etc. Only big exception off the top of my head would be the nicer koni dampers and some well designed springs with proper rates taht don't drop the car too much.