I'd like to see one report that shows categorical sales as a percentage of total sales (like in the Margin Detail Report under Filter by Sale Value), with a column next to it showing the on hand inventory dollar amount and the percentage of total inventory on hand.
For example, if you have a category showing 1% of total sales and 30% of you inventory is in that category, you might have a problem! On the other side of the spectrum if you have a high performing category with a small amount of inventory (which can be good), it might be a growth opportunity.
This report would also be great for Brands (not just suppliers as we may get one brand from multiple suppliers) too.