The epoxy barrier might work, but in general encapsulated metals are risky because they are impossible to inspect for corrosion and cracking so fail without warning, and the encapsulation can block surface oxide formation which causes crevice corrosion- especially if small amounts of salt and water get in there, which they will over time, even in epoxy.
I’m sure what you are saying could be done- especially to basically add stiffness to key regions of a carbon racing bicycle, but it would be experimental and I would not trust it to last a long time
Not really- even very thick carbon is quite flexible…. It works great for applications where you want that like bendy sailboat masts and front forks on bikes, but it should be cored or replaced with something else if you are looking for stiffness
That doesn't match with my experience. I've got a carbon fibre road bike and some parts of the frame are remarkably stiff whereas other areas such as the handlebars have noticeable flex.
It can be surprising to people just how tough/strong carbon fibre parts can be - here's Danny MacAskill's destructive testing of some CF wheels: https://www.youtube.com/watch?v=VfjjiHGuHoc
I’m sure what you are saying could be done- especially to basically add stiffness to key regions of a carbon racing bicycle, but it would be experimental and I would not trust it to last a long time