> I'm thinking of "machine-pickable" as the natural next step for growers to aim for.
> Is this already being done?
This is, indeed, already something that is done. As I understand it, for tomatoes it's typically for canning varieties, but they're called determinate cultivars[1]. Even with those, I know in processing you still have to discard the occasional fruit that isn't ripe.
I imagine this kind of technological solution would also be more useful when picking tomatoes for use as the fresh fruit.