Welcome to the Community, rsteph.

I can see how beneficial how this option(change the default COGS account not only in the "Purchases" account) would be beneficial to your business. I'll be sure to take note of your feedback and pass this along with our developers. 

We take into consideration our customers’ ideas when enhancing the product’s features. This would be helpful in identifying our customers want for future enhancements.

I encourage you to visit our QuickBooks Online blog regularly. From there, you'll be updated with the features and enhancements that our developers are currently working on.

You can also check this article about changing product and service item types in QBO for your guide.

If you have any other QuickBooks related concerns, you can post them anytime here.