Not for A18 with A19 being so close. I cannot rule it out for A19, but it currently is not on the roadmap for me. Separating the zombies from the core is not easy and if I would do it, it would become a seperate modlet the core would use as well. Gnamod does not just mix up things a bit, it is a total rewrite of entityclasses.xml, spawning.xml, gamestages.xml and spawninggroups.xml for the zombie and animal bits alone. They also use bits in other files to work.
But there is always the off chance in the future for me making modlets that contain watered down features from Gnamod Core, such as a Block Shape pack, zombie rewrite etc, but the way I generally make this (total rewrite) makes it incompatible with other modlets and I do not really want to deal with people getting upset because a Gnamod modlet does not play ball with their other favorite modlet.