hi,
to avoid to much customization i suggest following process:
to add drop shipment at quote level and creation of a purchase quote out from the sales order incl. correct connection between them and the then created orders would be a greater change. drop shipment at quote level makes no sense anyway.
so better you start in general at order level to stay nearer at the standard, means:
* create sales orders instead of sales quotes.
drop shipment is available at order level, you can create a purchase order directly from a sales order.
additional orders can also be deleted like quotes, if there were no posting actions. so if an order is not accepted or needed, then simply remove it.
* so how to get the needed quote reports?
create report "sales quote custom", which uses the data from the sales order. copy the layout from the standard "sales quote" report. send that report as pdf to the customer.
create a report "purchase quote custom", which uses the data of the then created purchase order (on base of the sales order with direct shipment). use the layout of the standard "purch. quote" report.
* add a new status value e.g. "Offered" to the sales order. the status is the field with values open, released, etc. this status should be set, if the sales quote custom report is printed/sent. if the ok comes back from the customer, the status should then be set to released. then and only then a sales order can be posted -> sales invoice/shipment.
do the same on purchase order side.
* i suggest you talk with your vendors about electronic delivery of the price data using webservices or EDI. that would optimize your price finding processes tremendously.