It would be very handy to remove and add fields that are searchable with Quick Search. It would also be nice to be able to extend this to custom fields added by other extensions. In order to accommodate this and re-use and already handy feature, adjusting this using Profile Customization is a great route to get this to apply to custom fields as well.

Could restricting the number of fields improve performance here as well? I have no clue, but we're always trying to make the SaaS version perform as quick as our old on-prem. version.