I'm butting in here without a lot of knowledge or training, but it strikes me that planet formation looks a lot like weather, in terms of complexity. I'm not sure how you could expect to model it without a lot of histories on which to base your model, and even then, complexity would overwhelm any particular run of your model.
I'd agree wholeheartedly, at least insofar as I think looking for a single model for all planet formation probably is wrongheaded.