I’d be more interested in the first problem as well – namely being able to change the size at which the thumbnails get generated, not inserted into the page.
The iImage plugin did that great in 1.5.x. During the upload process, you just had to click if you wanted a thumbnail, and you could give it a different maximum side size in pixels for every image.
So what I’d like to see is the option to create a 266×200, 400×532, or any other size I may want that one time thumbnail, instead of a certain fixed size. (Or at least the option to set the one size easily for my blog-the default is way too small I think.)
And sure, we could use the originals and the width height tags, but we have thumbnails so people don’t have to load the entire pic if they don’t want to see it, right?