Allow site configuration of number of optional fields of various types. Let the deployer decide if they are willing to take the performance hit.
Add options on the "add custom fields" dialog:
1) to indicate if a field should be "searchable" (include on search criteria page). Could be a checkbox just like "optional"
2) to indicate whether it should be shown on the "summary" page.
Something was mentioned about "tags" in one of your forum responses, but no depth was provided or expected release of that feature.