You could try customising the BOM template, but I have a feeling SW will not play nice with the extra rows before the column headers.
I'd put my energy in creating a macro on excel the inserts the extra rows and data.
Yep. I Tried to Insert and format it. SWx not allow to do better formatting.
I think we need to depend some Macros
The only way is a macro or dare I say an addin.