I have not looked lately, but perhaps there is a WYSIWYG editor with similar functionality?
I’m actually coding one for an upcoming project, so far it does not work in webkit browsers as I’d like. I’ll be sure to put it on devot-ee when it’s up to standards (probably 3-5 wks).
In the meantime you could handle this with some regex action as Jamie suggests with php (on the output stage). The problem with this method is that it will occur after the rendering of the page and you cannot simply replace the image tags with EE for imgsizer, so you may have to use a more traditional image-sizer or one that allows you to specify dimensions in GET variables.
Something like: (pseudo code)
<?php ob_start(); ?>
Insert your exp:channel:entries loop here
<?php $haystack = ob_get_contents();
ob_end_clean();
echo preg_replace('/(img|src)("|'|="|=')(.*)/i',"/imgrenderer.php?image=$3&height=100&width=100",$haystack);
?>