Hi Tim,
Are you still working on this - haven't seen a response since you originally posted it? If you don't mind I have a couple of simple questions that others might also have:
* Is this to be used within a single domain or are you thinking cross-domain functionality (like a CDN)?
* You used the word "plugin"...so would it be relegated to be used only from within CMSB sites/functions, outside, or a combination? I am wondering the process here for prompting the need. For example, I have a client that uploads an absurd amount of photos to his site via the standard CMSB functionality. IF he were to be skilled enough to utilize a higher speed uploading process such as FTPS he could save exponentially on upload time.
There's another potential here in this concept. Image uploading has always been a challenge because of the very nature of the file types, etc. (remember not too long ago the challenges with flash uploading being dumped, etc?). If the image filenames were pre-configured into either/both the CMSB code/php-html code then having a separate high-speed upload/storage system could provide quite a few advantages for speed, storage, security and probably price.