I wouldn’t personally use the word abandoned, but it is unlikely this will be implemented into the core SimpleCart package any time soon. There’s a can of worms that opens up when you consider people may use multiple option TVs, as then you need to figure out which one to use as leading. I’m also not sure how this would work in the checkout, but I haven’t looked into it specifically yet.
It’s not an impossible request, especially when setting clear expectations for what is and what isn’t supported, and I can see there’s still demand for it, but my time is limited so I don’t want to create any unjust hope for it to arrive soon with most of my time going to Commerce these days.
If @matdave were willing to share his code, that could be useful for the people here I’m sure.
As for Commerce, the way Commerce deals with this use case is that each unique variation (e.g. “Red t-shirt in size S”) is a unique product record, with its own pricing, stock, weight, etc. That has the downside that if you have lots of dependent variations, it gets exponentially more work to manage, but it is more realistic in the sense that for most types of products you do in fact have a separate stack in your warehouse.
Products in Commerce are also extendable, so while Commerce doesn’t currently have the concept of product attributes, adding that into Commerce will be much simpler than it would be in SimpleCart.