how to allow external off-site image embed in forum posts?

I'm trying to give my members the ability to embed off-site images inside forum posts, specifically with the following features...

• forum posts
  the ability to embed images in all posts, specifically forums, and not just CCK content
• formatting/thumbnailing
  the ability for admin to control the size of the embedded image, something like the very good embedded media module does (but that only works for CCK content). I don't want to just allow the <img src=" filter because then they could include images that are too large to fit my site width, etc.
• off-site embedding
  the ability for members to embed off-site images directly. I don't want to have "upload" module dependencies because a lot of my members already have lots of photos hosted on other sites, like Flickr and ImageShack, which do it well and I don't want to duplicate their functionality or require members to re-upload them to my site

Does anyone know the best way to do this, or if there is an input filter or other module that allows off-site image embedding with the above features?

I know there are individual modules for Picasa (http://drupal.org/project/picasa) and Flickr (http://drupal.org/project/flickr), but I'm looking for something more universal (e.g., PHotobucket, ImageShack support) and simple that allows the functionality of the aforementioned Embedded Media Field (http://drupal.org/project/emfield) or IMG filter (http://drupal.org/project/img_filter) modules but for non-CCK posts (e.g., forum posts) and no upload dependencies.

Thanks,
KV