Great tool, I think attributes should be weighted according to their correlation to growth. Also find correlation between attributes, i.e growth for theme vs growth for mini figures. Then weight this in as well. For example, the growth for theme and growth for mini figures has a low correlation for Lego city but high for Star Wars.
Great idea, I'll work on that. I also want to factor in things like sub theme too. Generally sets that are the first set in a new sub theme (e.g the Star Wars helmet sets) do really well later down the line when people want to collect all of them"