1) I have heard from FileMaker personnel that the total number of Table Occurrence boxes can negatively effect performance.
2) The more indexed fields you have, the more records and thus the larger and more complex the indexes become...
The longer it takes to do "mass updates" such as Replace Field contents on a large block of records or Importing a large block of records into your database. It's very unlikely that there will be a noticeable "hit" from modifying the value of a single field in a single record.
The more indexes that you have, the larger your file becomes as well.
Thanks for your information. I will use this information and keep this in mind when developing the extension.
Thanks again Phil,