It seems like setting the purchasable hardpoint cap to 11 would be the best option, not only because it’s a fairly reasonable number of max slots but because adding it with the number of slots in the H&C 101 (1) gives us 12, which is the maximum number of hardpoint slots that could be added into the hardpoint section like this:
Adding any more slots would require a reduction in the size of the slots which would make reading things more difficult and besides, 12 slots are enough for 95% of players when it comes to decorating their ships.
As for the price, aside from the laser scope which helps players in terms of accuracy, the other two hardpoints are just cosmetic features. As such, they should be more expensive than a Color Theme but less expensive than an Extra mission slot.
In my opinion, 180 keys should be the price of such hardpoints, that way, you still have to spend 1980 keys to allow all ships to have 12 hardpoints. But of course you can come up with your own price if my proposed price is too expensive/cheap.
Be sure to let me know your thoughts on this and may the Forks be with you all!