To have a switch control the amount of air/fuel at any given throttle setting, you'd need completely electronic throttle control (fly-by-wire), which you don't have and a chip to control it all.
If you want to avoid accidentally pinning the throttle to WFO (wide-f&^*ing open), design some sort of throttle stop that you can engage off-road. This is what the mini-bikes have so parents can regulate their kids hoolaginism.
Turbos are suited to v-twins, and kits are sold for Harleys. The expense of developing an exhaust and intake system, as well as almost certainly needing larger intake manifolds, waste gate, intercooler, electronic control/ignition would make it daunting.
With the boost set to "low", you wouldn't have normal DL650 power, you'd have DL1000 power, and with the boost set to "high" you'd have Ducati 999R power...a 160hp DL650 would be a blast for the 7 minutes that the clutch survives.