Modifying a laptop battery to increase capacity?

Question

laptops

The laptop's acc died, googled the replacement of 18650 cans, thereby returning the acc to life.
But the thought arose: what if you use an account controller, but connect not 2 or 3 blocks of 3 banks to it, but much more? I do not know how these controllers work, but I assume that they rely only on the voltage of the connected cans. This means that you can take not 9, but 12/15/18 cans, chain them into blocks of 3 pieces in parallel and connect the controller in the same way. The graph of the change in voltage over time, in theory, should greatly spread horizontally.
Question 1: If my theory is correct, what problems might arise here?
Question 2: There are thoughts to update all the banks in the main battery, and to increase the capacity in the laptop case itself, instead of a DVD drive, push flat batteries with similar parameters and connect them in parallel to the controller in the battery. What problems exist here? In my opinion, only the identity of flat and 18650 batteries according to the graphs of voltage changes over time at different currents.

Answer 1

Even the "simple" replacement of cans with similar ones is not so simple. For example, the battery controller can see that something is wrong and turn the battery into a pumpkin. Not to mention the increase in capacity.

Answer 2

Google "laptop battery repair and refurbishment" and you'll get answers to all your questions and lots of ideas.