Strictly my opinion here, but...
you could use limiting straps to prevent the suspension from fully unloading.
you could replace the bump-stop on the upper arm with a longer one to keep the suspension from fully unloading
you cold purchase shocks which will only extend to the point where the spring is "still not loose" and hope not to "extend" the suspension very quickly (hitting either end of shock travel has some consequesce over time)...