I think I would encourage my son to do it if he could work it out with school. A semester in Europe, working, is a pretty exciting life experience to have. Assuming school will be there, it seems like an easy choice to me. Again, assuming school would cooperate. My daughter just finished her first round of (14!) musical theatre audtiions over the last three days. It’s not that unusual for an MT student to take a bit off when an opportunity to tour comes up. I like that idea. They want to be working artists - that’s why they are in school. So be a working artist!
Also, I bet he could find a way to pursue upright while there. Maybe ask about an exchange opportunity? You never know what can be worked out until you ask. Or better yet - make a plan and present it. Good luck - I can’t wait to hear what he decides.
Sorry - just saw the bass teacher’s response. Sounds like you have an answer.