I am no expert on Hull Reinforcement or Module Reinforcement but if allowing more 'smaller' slots by splitting larger slots would 'break' ship balance then these modules could just be 'hard' limited.
Are 'bullet sponges' necessarily bad? If people choose protection over flexibility that is their choice. As I have always said MORE choice is almost always a good gameplay thing.
Well, they are not hard limited. And people would use them to make them bullet sponges.
As i said, having limited internals it part of the ship balance, along with flight characteristics.
Not at last, More choice is a good thing when there are negatives and there is a balance between the Choices, else the best choice will eliminate any other choice and... well... you get the picture.
You state that 'some' ships could use extra internals and I would argue that virtually all of the smaller ships (Asp Explorer) down could do with 'extra' internals depending on what you are trying to build. As far as I can see the only smaller ship that actually works as a mining vessel for instance is the Cobra mk IV.
No. Most ships are ok as they are
My 2 examples (T10 and Clipper) have what i would call a reasonable case for them to have some optional internals added.
T-10 is the heaviest ship out there, yet i can carry barely more than a Conda - the lightest big ship. Why? because when T9 got an extra size 8 internals, making it a very good hauler, similar to the Cutter, but at a fraction of the Cutter's cost and without being rank locked... T-10 got nothing, and it should have gotten a size 7 internal.
Same for the iClipper - it's a large ship, but with lesser cargo capacity than a Python and with slightly more capacity than a Krait mk2. Another size 5 internal would bring it more utility.
AspX? It's fine as it it.