Gamerule to change Zombie Villager conversion rate

Me and my friends have been debating whether we should play on Hard or Normal because of this, as they don't want to play on Hard I've been thinking about a different option to adjust the conversion rate of zombie villagers. Mods exist, but would 1. require setting up the 3rd party server again and 2. couldnt be done on a Realm. Datapacks simply dont exist (apparently due to the logic for zombification being in the source code). So I figured a simple gamerule that allows to adjust the precise percentage of zombification rate would be nice.