I think it would be good if people could configure the cost of their payment processor - ie. % fee & transaction fee.
At the moment some payment processors return this information when a transaction takes place & it populates the payment details but others don't.
The benefit would be for reporting - e.g. the EventAggregate custom search has hard coded transaction costs in it but the code would need to be hacked for a different processor with different rates. Plus if an organisation changes processor then the rate could change.