We have models for estimating the probability that a block is orphaned given average network bandwidth and block size.
The question is, do we have objective measures of these two quantities? Couldn't we target an orphan_rate < max_rate?
Models can predict orphan rate given block size and network/hashrate topology, but you can't control the topology (and things like FIBRE hide the effect of block size on this as well). The result is that if you're purely optimizing for minimal orphan rate, you can end up with a single (conglomerate of) pools producing all the blocks. Such a setup has no propagation delay at all, and as a result can always achieve 0 orphans.