I think if one is skilled in something it is better to stick to that. However, than no new skill
What is a shore hardness of printed stuff, Epoxy and PU?
Graphite is not great, you'll have it everywhere on hands and rope.
When u bend a bar that insert will not add anything to bending resistance in any axis. There will be a chance that carbon will crack where the bolts are, when is bent. Plus, seeing smaller hole protruding from the insert, that is impossible to place inside the tube.
We need something glued in the middle for 2 axis. It is metal we are replacing, correct?
Metal has resistance in all axis, carbon hasn't. So the best would be Alu cylinder but coz corrosion, it is a no go.
D.