A few interrogations I have - without having the necessary background:
Why do models for the formation of our solar system suppose that all heavy atoms come from a single supernova nearby? Several events producing separately the chondrites and the siderites would ease many questions.
Why do models suppose that the Solar system started as gas? Does something imply that a supernova explosion produces only gas, including of the heavy and refractory elements, and that the solids appear only when a planetary system condenses?
These two would not need the solids to differentiate in a planet big enough, nor would they need said planet to be destroyed, to explain the diversity of meteorites. Current models have some difficulties with that scheme.
As well, I nearly believe (have check some figures) that gravitation can be extremely efficient at separating elements and isotopes during some stages of the formation of planetary systems. The potential is more than sufficient: at Earth's orbit, one neutron more means about 500 times 300K difference in kinetic energy, so in a gas, the settling would be extremely efficient, much better than anything humans achieve in a centrifuge. The only question is whether at some epoch, the elements exist as a gas, and dilute enough that diffusion is quick.http://www.physicsforums.com/showthread.php?p=3439127#post3439127
Some observations see oxygen well spread at the very beginning of a planetary system but disappeared at systems but older, which my proposal explains easily.
Such a process would need to re-think the arguments based on isotopic abundance.