I’ve done a lot of research lately on rib injuries and possible exercises to strengthen the intercostal muscles like you mentioned TJ. Problem is you cannot really isolate this muscle group making it hard to build up the area. If you notice the back of your rib cage does not have much muscle covering it, making it difficult to protect against excessive force.
I did side planks and specific exercises to target this area for about a month straight and didn’t see a change on track (comfort wise). That was my plan A to fix my rib problem. Now I am on to plan B which is the padding.