I think the OP was asking if there is any reason he can't put a different battery into the connections on his bike and ride off into the sunset. The answer to that is 'Yes, that will work', as long as the polarity is right and the voltage is right, and the electronics will integrate with the new battery.
In other words, one could buy a battery from Paul at EM3ev. A trusted vendor. You can mount his batteries in a bag on the top tube. If you run the wires to the original connections, leaving everything else in place (circuit boards, etc) it should work. If the original battery pack has more than the plus/minus connections, stop there. You can't recreate those monitoring connections.
Rebuilding the pack would make more sense than chasing stuff on Alibaba. The original design is going to be more robust, with better seals at the connections, if nothing else. On the other hand, you could move the battery forward and make the bike more balanced. It's sad that there seems to be one place to rebuild these packs. It's sad that the packs are not made to be rebuilt. It's sad that there isn't a more universal pack. I guess it is sad that the world's largest ebike company can't supply, out of inventory, a battery for a 3 year old bike. I mean, really?
So... Do what makes you the most comfortable. There are lithium batteries in every phone, every portable computer, every tablet.