Hrrm, that could cause problems. There isn't really a state of "being flanked" in the game mechanics. It's the misconception of such a state that leads new players to ask "Well, if those too guys are flanking the monster, then I should get a +2 to hit from over here right?".
The answer, of course, is no. And the reason is because your two friends are flanking the monster; the monster is only flanked with regards to them specifically. The monster is not "flanked" in the general sense, so the +2 bonus does not apply too anyone who is not actually in a flanking position with respect to him.
Your rule about feinting only creatures flanked by you "or other people" goes against this mechanic and might cause confusion by introducing an erronious concept. Just something to keep in mind (aside from the fact that you are greatly weakening the Feint ability).
The answer, of course, is no. And the reason is because your two friends are flanking the monster; the monster is only flanked with regards to them specifically. The monster is not "flanked" in the general sense, so the +2 bonus does not apply too anyone who is not actually in a flanking position with respect to him.
Your rule about feinting only creatures flanked by you "or other people" goes against this mechanic and might cause confusion by introducing an erronious concept. Just something to keep in mind (aside from the fact that you are greatly weakening the Feint ability).