RE: The Competitive Battling Simple Questions Thread
There are many things that are straight up not viable (mostly due to being outclassed), but unpredictability can change battles to some degree. It's not easy to control, but essentially the best form of unpredictability is to be able to out-predict your opponent and make choices accordingly. Custom sets or not, you have to know your team and be able to determine what move your foe will chose well in advance. With stall teams, defensive planning makes tactics like move-baiting easy to pull off and you can get away with much more 'unorthodox' shenanigans since you'll usually focus more on indirect damage than straight-forward attacks (hence the observation that stall teams success comes from 90% from design and 10% from actual execution).
Buffing attack and passing to Espeon is a horrible example since (1) Baton pass chains generally don't work against experienced players and (2) you wasted the boosting turns and left yourself vulnerable when switching to Espeon. There is literally no way you could turn that 'unpredictability' to your advantage without getting uber lucky.
What does work, to some extent, is taking a gimmicky strategy and devoting the rest of the team to patching its weaknesses or removing the normal counters (note: this is EXTREMELY hard to pull off and I've only done so once or twice myself, only to net very little improvement in win-rate above 'normal' competitive teams). While it may not seem worth it, I actually recommend experimenting with gimmicks after you get a firm grasp of game mechanics and most competitive principles, as it helps you not only prepare for unexpected sets with your own teams, but also forces you to experiment with pokemon and moves you otherwise wouldn't. Occasionally one of the gimmicky sets (or something you design to cover a gimmick's weakness) will prove useful in more orthodox settings as well, and that's when you can truly get better as a player. A prime example of this is my 'Vegetasaur' set (seen in my
latest RMT). Originally designed to be a gimmicky, bulk-oriented Mega Venusaur, it proved easy to set up with and could cripple a large portion of an enemy team while dealing with many of M.Venusaur's normal counters easily (with good prediction).
Predictability is a slight disadvantage, but if the set is efficient, it doesn't matter all that much. Even 'unpredictable' sets have to reveal their moves sometime, at which point they lose all advantage they had with the element of surprise. It IS possible to win a battel due to unpredictable sets alone, but doing so is not consistent. Almost all of my 'good' teams (even gimmicks) are primarily standard sets, with only a couple pokemon with either modified or custom sets, designed to turn the tide at opportune moments.