Sure, but if you limit them too much you reduce capabilities and things like endurance. And say 36 small submarines could easily be a lot more expensive than 8 medium-sized ones. As I said, you need to remember the cost of the components, as well as the cost of training and paying the crews.
They could investigate the possibility of making their own drone subs.They could be used in what one would refer to as suicide missions.
Reliable and continuous comunication with the sub wluld be the tricky part I guess.