It would be great to have a command-line option to make all ftp connections expect filenames in UTF-8. This would make aria2 send OPTS UTF8 ON, and then the aria2 user could ask for filenames percent-encoded according to the character's byte representation in UTF-8.
Is there any specification of OPTS UTF8?
I found http://tools.ietf.org/html/draft-ietf-ftpext-utf-8-option-00, but it was expired