The Magento system for product variants seems a bit back asswards, but is workable for now.
What doesn’t work is when you want to use inventory tracking in situations where you have a single product in inventory that gets split up into smaller pieces when a product is ordered.
Ex. I have a spindle of Rock Textured Fabric (1000ft in inventory). A customer can then select 5-35ft cuttings from a group product page. The issue is that when it is purchased, the inventory goes down for this individual simple (sub)product, not from the entire spindle. What a headache.
There should be a method to link a products to another inventory and remove the appropriate amount when it is purchased and use that number for inventory control/alerts.
This would be a GIANT boon to people who sell bulk materials and want proper inventory control.