So, sort of what I’ve done, but shooting for a different binary alloy.
Provided it can be done, the one possible drawback I see is that it’s committing your pure source materials to a specific mix. In my case, I use several hundred pounds of just one casting alloy yearly, so dedicating 10-20# of tin/pewter to mix irretrievably with Sb isn’t a problem. But I still keep the bulk of my pewter and pure tin unalloyed because it’s much more flexible that way, not to mention more sellable.