It would be really quite useful to have the option to retry failed submissions 'x' amount of times.
Often the fault is a bad captcha answer, temporary proxy issue or other thing that could work on a second attempt.
It would need to 'forget' any data associated with that url (such as assigned proxy, username etc) to avoid being detected on the following attempts.
I dont think this is likely to be a confusing option at all, but if you feel it would be, having it as an engine switch instead would be fine, eg:
retry failed submissions=3
This is especially useful when using ocr like CS, as a retry doesnt cost anything.