There is an feature described here, for upload:
https://forum.tixati.com/support/584/
For the duplicates, there is the official protocol and message trading: BEP 3
http://www.bittorrent.org/beps/bep_0003.html
https://en.wikipedia.org/wiki/Glossary_of_BitTorrent_terms#Choked
As we have the chance to choice, the "computer" does too, so it is part of the BitTorrent, that good implementations will make good and healthy algorithms that will not suck balls out of the whole peer list.
Making such a change, is out of the protocol recomendations, and will of course, make one peer priority over all others.
This means, ganancious (for seed or peer?).
If you want to break the rules, do it manually, or else increase the number of simultaneous connections.
Or else, make your own BEP recomendation, make it Bittorrent official, with this scientific article that will deny a lone dev: