Options to Set Margin % on Sales orders

Please look at adding a feature that allows you to change in system settings, how the margin % is calculated against a product entry on a Sales Order. Currently there is no choice other than 'Average Cost'. This is not very useful  especially when pricing up Tender submissions that typically are very low margin, so the ability to have 'Last Price Paid' or even to select a batch that may have a lower buy than others would be appreciated. The system allows for a similar setting for Purchase Orders (with at least the 'last supplier price' paid option) - but not for Sales orders. A further point on this would be a feature that would allow you to manually add the buy price against each product line entry on a Sales Order at quote stage - a useful tool to help negotiate special 'project' buy pricing with suppliers after you have complied a quote with target sell price.