While that would make things more convenient, there is little to no loss from having extra, yet there is potential for loss from having not enough. If you calculate it so it gives you the exact amount required, it reduces the length of time someone can hang with a fully charged drive. Whether someone is AFK, or not acting fast enough, they could end up losing their ability to jump because of it.
Additionally, if they jump they still have the left over batteries that will reduce the cost next time. It should also be noted that if they jump into a restricted system (one that kills them instantly) they will respawn will all their batteries and cargo intact due to the way the plugin handled those systems.
Edit: In response to this:
(03-20-2018, 09:50 PM)Remnant Wrote: While you're at it, just make an option to enable it. (/autobuy jump on)
I propose just renaming cloak to special and then removing the word cloak from cloak batteries. That way all FLHook items can be controlled via one autobuy list, which would eliminate the requirement of creating multiple (that ultimately do the same thing).