We did try and implement a 'grace period' but it just proved difficult with the game engine and there were technical complications that proved difficult to get around.
In terms of buffs we did consider it (not allowing any outside buffs), but felt that overall, using buffs is such an integral way of tweaking, especially in PVP, that it was better that the duel system allowed players to prepare buffs before the duel. We couldn't do both, so we went for the option that we felt was most in keeping with the way that people who enjoy that type of PVP usually play.