It takes a long time to design and fab new layouts. So at best you would get firmware mitigations baked in. Or, as mentioned in other comments, the HT sidechannels might be fixed simply because HT is turned off.
I found out that the author had a lot of free time (otherwise, how can you justify the learning/testing the platforms?). That is incredibly good for himself to learn all of them but seriously, why?
Fixing unsafe code is much easier and safer in the original implementation than a rewrite. Even adding critical features is. Never the believe the rewrite and throwaway apologists. They have done enough damage already.
