It sound like a job for Photoshop scripting to me. Photoshop can be scripted I don't use any other Adobe product but I know some can be scripted as well.
I only remember save as requesting conformation to overwrite a file.
If you record a save as step in an action and change the file name field in the save as dialog the name would be recorded in the action step. The step would always save that one hard coded file name. If you did not change the file name field in the save as dialog no name would be recorded into the action step. When the step was played the name would default to the current document name.
The file Name field is a single field with a pull-down that you can select previous file saved full path and file name. I never remember more the a single field in the Save As dialog for file name. Here are the two Windows Photoshop CS2 save As dialogs. The OS Dialog and the Adobe Dialog. I still have CS2 your CS3 statement and prior versions. I have often recorded save as steps in action. Never seen an option of creating sequencally numbered file name other then Automate Batch and Image processor.
