I mean I dunno, even if you switch to some sort of li-on AAs (something which I think would also be good for other reasons, like making recycling potentially easier, being able to swap batteries between devices, making batteries slightly cheaper), I dunno how many people are gonna want to slice open their own batteries and run tests on what comprises them. Since the half-life on any given set of batteries is probably in the range of multiple years, or at least several months, you’d probably be able to set up an attack before any government agency or private battery replacement or analysis would start getting off the ground to sus out what you’re doing.

I think the only reason this might be harder with replaceable batteries, would be that the potential for batteries to get swapped out of devices means that you’re less certain to see any kind of explosion from a given device that you’ve modified, and you’re less certain to hit the particular targets that you want, but it doesn’t seem like either of those would really be a big problem for whoever would want to do this sort of terrorism in the first place, so I’m not sure that’s a major deterrent.