Honestly, I do not see this as a big issue. The GasGas parts interchange between years and also with other bikes is very good. Consumable parts with a new second source (some are other than OEM): plastic, drive chain, suspension bearings, suspension fork and shock parts, trans bearings, kickstarters, shifters, levers, foot pegs, gaskets, clutch baskets, pistons, rods, etc are pretty easy to source by other companies or from crossover with other bikes.
I think that leaves us with a pretty short list of parts that we need to have from the factory.
No second source for new replacements - Engine cases & covers, transmission gear sets, crank shafts, frames, airbox and air boot, subframe, triple clamps, clutch hard parts minus basket, powervalve parts, axles, swingarm, shift shaft, ???
Lots of used parts are available as many people part out their GG bikes because the resale value is not so high.