I've heard gmail's data store makes this an expensive operation. It doesn't want to load all your messages and sort/page through them by their content. But can't give you a citation on this.
Presumably, this is why all views are chronological: it filters a time-indexed stream of messages.
I don't buy this. Gmail allows you to sort/select using other parameters. This would simply be another search param.
Note that I'm not disputing the fact that this may be an expensive operation. But I am able to go in through IMAP and issue the equivalent instructions, sort by size in client, then issue IMAP delete/purge requests, the net result is the same so why not enable this.
Add the ability to sort by attachment size. I want to be able to clear out some old files and have to resort to attaching Mac Mail to it just so that I can sort.