This is exactly how I would see the plugin working at the backend.
Here is a recent BBC Blog regarding the new qualities of BBC iPlayer streams available
BBC Internet Blog
I know that the current work recreated the whole iPlayer flash instance, is there a way to get the flash video behind the whole flash player instance and play this through MediaPortal's internal player?
EDIT: Re-read cheezey's post - I realise now that it is possible to get to the mp4 files made available to iPhones. These, I imagine, would not be getting a 'quality boost' and would stay at 800kbps. No access to the 1500kbps (SD) or 3200kbps (HD) would be accessible using this method...so the flash route may be the best way to get the best quality.