Unless it's specifically stated how much of a % of changes needs to be done, then any changes done constitutes a change. 

Thinking with my vendor cap on here...... As a vendor using a resource, I would want to make as many changes as possible so that I could feel that it is my own work.  But that gets into morals and ethics.

Thinking with my buyers cap on here....... If I were to purchase 3 character packages that all used the same resources, and found distinct similarities in them, I wouldn't be a happy customer.

If resources were REALLY used as they were intended to be used, this question would never arise.  A resource is only supposed to be used in bits and pieces, but the way you're stating here, it's not being used that way, and it's a shame because the vendor will suffer because they do not allow their own creative talents flow into the package, so in my eyes, it's really not their creation.

Debbie M.