Alright I gotta vent I am losing my head over...
The child has learnt a new way to play where they smash TV remotes on to the ground, it comes apart and then they proceed to chew on delicious AA batteries. The child's grandfather who takes care of the child for a significant period of time and who has put little to no effort in childproofing the environment, has ordained that this is fine.
The child's parent has tried asking the grandfather to not let the child do this. Until last week I hadn't imagine that one would ever have to labour to explain why a child should not chew on batteries. But seems like they are unable to have a rational conversation due to being emotionally stunted which I guess runs in the family.
Really looking forward to the day when I don't have to deal with my family (except the child) anymore.
Your second suggestion seems dangerous but the first one has potential. I will put masking tape on the casing. It's easy to remove and will probably stop the child from taking the batteries out.
Less secretly...
if you can find a fairly small screw and a really thin dril bit, you can try to use that to keep the remote closed in a way that the battery place can be accessible in the future.