There is a SuiteCommerce Extension, Custom Fields, which permits you to add display fields on the PDP from the item record, but also add transaction body fields in checkout.
The request a quote button is an alternate path in the shopping cart, where instead of creating a sales order, it creates an estimate. I think the gotcha with that extensions is that it might add only to the sales order.... or if it adds to the quote at all, it would also add to the sales order. You might need a custom extension to add just to the estimate without also adding to the quote.