If you mine in a high enough high sec system, one light drone is enough to handle the rat frigates before they can be troublesome (break shield on a minimally tanked venture). Given that the venture has enough bandwidth for two drones, it would be worth trying one mining drone + one light drone if that combination would be available for alphas. Some will use two mining drones and get in trouble with rats, some will continue to use two light drones and have lesser mining yields.
Who are we to protect alphas from themselves? Making (sometimes costly) mistakes and learning from them, that’s the point of EVE, no? Currently, drone wise, for an alpha mining in a venture, there is no choice: you’re using two light drones. Enable civilian mining drones and suddenly you have one, and one that can actually have consequences (ex.: getting popped by a lone rat while afk ratting because you had 2 mining drones, but also improving yield a tiny bit if you do take the risk).