I just found out that my download speed increased by 4 folds whenever I had a peer from my own country (same ISP to be precise). Being able to prioritize the peers of my own country first could help boost the download and upload speeds for both me and my peer.
I think all clients do this but in a different manner : they prioritize by download speed. No need to lookup each and every IP and see if it's geographically close to you, if the speed low. They could also have settings that prevent their client from uploading with more than x KBps.
utorrent : https://superuser.com/questions/431417/can-utorrent-auto-re-order-torrents-for-maximum-bandwidth-utilization
qtorrent also has this ability : https://github.com/qbittorrent/qBittorrent/issues/1957
also a guide : https://torrentfreak.com/speed-up-your-torrents/