My wishlist:
The ability to set custom values for other return results from a payment provider (preferably in the CustomValuesXML field in the Orders table of the database).
Right now, you can save the AuthorizationTransactionId, AuthorizationTransactionCode, AuthorizationTransactionResult, CaptureTransactionId,CaptureTransactionResult.
For handling things such as:
Extra IDs (like in Intuit Merchant Services, there is a separate ClientTransID value that is used for banking reconciliation in Quickbooks)
Transaction timestamps from the merchant bank - these are used to confirm valid POSTs if a security issues ever comes along (like a hack attack).
I'm writing a comprehensive Intuit Gateway Payment Module for the community here to fill the vacuum of Quickbooks support (or shall I say, "affordable" Quickbooks support)