Let's look at it this way, what are the chances you'd actually load up the rear enough to make it sag to the point that the cone bump stops (before being man handled by you) would actually make contact to the axle? At that stiffness and ride height I would imagine that would be highly unlikely. Which brings me to my final point, if they are never going to touch, who cares if it's there or not
I don't see removing those being that big of a deal since we already have those bump stops (by the inner fender well) that prevent the rear axles from flexing upwards too much and bottoming out the shocks. Maybe if that cone thing was the only bump stop in the entire rear suspension, then i'd be apprehensive about running without them.
Since you already have the rear springs ready to go in why not just put it all together as is and do the flex text with the fork lift to see if you can even compress the rear enough to make the cones touch. At least that's what I would do if I was in your shoes; I'm a cheapass when it comes these little things.