I personally like the idea of Harvest as CAP's secondary ability. Harvest, while not inherently risky, does inspire risky strategies such as pinch berry abuse, custap berry sweeping, and resistance berry abuse. The first two require that our bug be at less than 25% health to work, which means that if SR is up, this will be the CAP's last stand. you take the risk of allowing one of your pokemon to sputter to a quick death due to low health or the reward of sweeping the opponents with ease thanks tothe repeated boosts provided by harvested pinch berries. The resistance berries force you to play a game of chance where if your opponent doesnt have the appropriate SE move, your item and ability become completely useless. Finally, if you want to get any utility out of harvest, you have to sacrifice your item slot to support the ability, meaning no Life orb or lefties for you, which would be a destinct disadvantage of trying to abuse this ability.
Harvest syncs pretty well with weak armor since both abulities allow cap to occupy different niches and harvest doesn't mandate any overly specific spread to be effective as weak armor does. This allows our stat spread designesrs more freedom to make sure weak armor is an effective ability while still offering another unique, risky ability to explore.
Did You Stand Too Close To The Fire?