I've managed to make the "detect file transfer plus or use standard messenger transfer" feature and it works,
but there is a limitation of Messenger/MsgPlus that do not allow you to send a file through messenger if there are more than one contact in the conversation window. I don't know yet if it will be possible to open a separate window (with /im for example) and then do a /sendfile in that window automatically. I'll post here any update on the subject as it become available.
EDIT: Actually it was a bug of my code instead
Also, the "separate folder for each contact" is implemented and working for Beta