You are close to the 100M Ethernet run length. Adding a relay along the way will probably be a mess.

I'd go fiber, a continuous run. You might need an assistant to help pull through the boxes, but the continuous run will be low maintenance over time. Check the Clearline spec. sheet. Notice how robust it is and check out the bend radius. Passing through the boxes will not be a major issue. You may have some trouble fitting couplings inside your boxes. That's one reason to use a continuous run.

After a little practice, you can terminate modern fiber faster than CAT cable.