Another "Implement this to save me some minutes" request.
Its not hard to do this on your own, and it wont take up less processing power simply because it runs through the client. The osr. files aren't videos, you know, why do you think they are single kilobyte sized. I believe they are nothing more then the data of how you moved your cursor, so in any case the client would have to either in the background or somehow magically record the whole play of the beatmap, which unless by the latter magical way would take no longer then if you did it yourself with whatever screen or game capture software/device.
Me and IppE already posted in your previous thread, you should consider reading it.