With Wordpress.org you can set your uploads directory to an absolute path, and modify the url information so that you're images can be stored on a subdomain. Very snazzy.
Can we do this in ยต somehow for the primary blog? Perhaps a constant or something we can redefine if $blog_id == 1
Even better in the future would be if we could add some kind of ftp information in and put them on a seperate site altogether should we like. But until then, I'd settle for knowing if we can even get them on a subdomain. :)
Just for reference with ftp you're sending your username and password in the clear. You may want to look into the use of sftp. Wordpress doesn't normally see ftp uploaded files, just the ones that go through the uploader. Would be a security risk as well since you would be unable to check the uploaded files extensions against your allowed list.
You can set the upload directory within your wp-config.php file. On one of our installs, this is pointed at a subdomain as those files are on a second server. I believe this is also how the amazon plugin works as well.
Just a side note, but I actually use sftp - I run ssh alone on my servers and no ftp daemon, I'm just not pedantic about saying sftp when talking about file transfer. ;)
What constants are we looking at in wp-config, WP_UPLOAD_PATH and WP_UPLOAD_URL? Or should I be looking at setting upload_path and upload_url_path inside of wp_1_options?
Thanks in advance @tdjcbe.
"Or should I be looking at setting upload_path and upload_url_path inside of wp_1_options?"
That's the route I'd try first.