How certain is it that a tokamak is even able to be run in a stable manner? What if it turns out that a stellarator would be better? Or is that already validated by now?
https://www.proximafusion.com/press-news/proxima-fusion-and-...
Problems are still many, though (Paper:)
https://www.sciencedirect.com/science/article/pii/S092037962...
I guess the biggest hurdle will be stable operation, without having to replace too many broken parts too often?
Tokamak requires regular shutdown as far as I understood and that is quite a lot of heat stress for all the parts I believe, along with the radiation etc.
(But I lack the background to really debate on the pro vs cons of tokamak vs stellarator, I just have opinions here)