Modifying config.ini for S3 Post

I am working on a plugin that calls an HTTP POST to store items in the Internet Archive's S3-like system whenever the item is saved.

I could hack a POST that using the plugin hooks, but I would rather use the methods already built into the Zend framework by modifying this Omeka adaptor:

Omeka_Storage_Adapter_ZendS3

Unfortunately, key parameters for the POST are defined in the config.ini file:

; Sample S3 cloud storage configuration
;
; The accessKeyId, secretAccessKey, and bucket options are all required.
; If the expiration option is set, files will be uploaded with "private"
; access, and Omeka will generate URLs that are only valid for a limited
; time. If the expiration option is missing or left commented out,
; uploaded files will always be publicly readable.
;
; storage.adapter = "Omeka_Storage_Adapter_ZendS3"
; storage.adapterOptions.accessKeyId =
; storage.adapterOptions.secretAccessKey =
; storage.adapterOptions.bucket =
; storage.adapterOptions.expiration = 10 ; URL expiration time (in minutes)

Is there any way a plugin could modify these parameters on a running instance of Omeka? I would like to use the robust built-in code, but buckets change with items, and I would rather not ask users of the plugin to directly modify a scary config.ini file.

Cross-posted on the dev list.