inconsistency in stock sku management and adjustment

PROBLEM 1:

When changing sku to adjustment or node, stock do not reflect the change: uc_product_stock has nid as a field and it is reduntant or it is not update with sku changes in no way.

Solution could be to update nid on every change, adding an hook, or to not rely on nid in that table using join with adjustments and/or node, and ultimately remove nid as unusefull.

PROBLEM 2:
Removing a node do not remove stock level, causing error when creating a new node with the same sku (duplicate sku in uc_product_stock). Given the inconsistency at problem 1, the solution would be to delete (before adjustment) all stock with used model.

Another solution is to force synchronization of sku. I am writing this but I need another hook (adjustments_updated). I'll post here the patch