Add a new item(variant) based on the template item

Hi All
When I add a new item(variant) based on the template item and I want to change (Default Unit of Measure) it does not allow me, the reason is that it takes it from the template clause knowing that I deleted this feature from (Item Variant Settings)
I know that it can be modified through other methods, but this method is the one I see fit
(for an industrial company (wires and cables) of various lengths),
Is there a solution to this problem .
Thanks to all