Project Management - Planning Resource UOM

I created a planning resource list that's centrally controlled, disabled "Resource Classes" . I added Financial Category as a Resource Format. And created 'Materials" as a Planning resource. This planning resource is mapped to the expenditure type "Materials". Materials expenditure type has UOM as Currency. However, this planning resource has UOM of hours. So when we enter a budget it's showing Hours as quantity, which is incorrect.

However, if I had enabled Resource Classes and Materials is defined under Material Items then it shows Currency as UOM. But doing this means Equipment, People and Material Items all classes are enabled. And the seeded Equipment has UOM of hours, while the Equipment exp type, we don't track hours. Also there would be more than one resource users can pick in the financial plan - Equipment as a class, or Equipment as a resource etc. We want to control such that folks can only enter resources that are one to one to an expenditure type, and further more only