We generally advise against setting goals this way because it is less predictable.
Not all products have the same potential for efficiency, some products will always perform better than account-level acos and some products will always perform worse. By setting goals as if all products are equal, we put account-level acos at significant risk.
Instead, what we advise is to set acos targets as close as possible to last 30 day historical acos for each set of products. This is the most reliable way to ensure a smooth transition between campaigns and prevent major unexpected fluctuations in account-level performance.
Once a goal has achieved 25-50 conversions, you can begin to change your acos target in an attempt to further "optimize" account-level performance.