This would require checking if we have at least 2 optimistic candidates and finding the previous one in the peer array to exclude it. In fact, [Transmission implementation](https://trac.transmissionbt.com/browser/trunk/libtransmission/peer-mgr.c#L3121) isn't doing anything to prevent this.

Also, when selecting the next optimistic peer with current implementation, we do no longer know which one was the previous (nor does Transmission).