Where profit disappears
Most scope fights start with a reasonable sentence: the subcontractor will provide a complete scope of work. The danger is when 'complete' means whatever the GC later wishes had been included.
For millwork, small details can be expensive. Site protection, rework after other trades, field-measure changes, blocking, sequencing, and freight can all become real costs.
Make the scope visible
Your proposal should not vanish when the subcontract is signed. Incorporate it, including exclusions and assumptions.
Then add a conflict rule. If the subcontract, drawings, specs, and proposal disagree, everyone should know which document controls before the job starts.