Well, that's just irritating.
I hesitate to suggest this, and I'll assume you've already considered it, but is it time to give up on the camera as a turnkey self-contained solution? If you're already ftp'ing, you're somewhat beyond that already?
Can your ftp server pull instead of push? rsync? script? (robocopy, if win based?) (Was it you in another thread unhappy that you can no longer get a static filename for the last snapshot? - script a directory watch and link the latest file to a static name, to which the cgi can point to?)
Or an external stream evaluator, such as zoneminder? (Perhaps in a vm?)
I haven't got one yet, myself, but I'm assuming from your comment that this is an ftp delivery mechanism limit, and 5K may not apply to other paths?