Tracking a specific Bitcoin to make it represent something else, which could then be traded without trust Imagine if one could follow the movements of a specific Bitcoin (or fraction thereof) in the block chain. Then that would mean that I could make that specific Bitcoin represent something else, which people could then freely trade just as other Bitcoins. 

For example, I could mark 100 Bitcoins and define that these represent 100% of the equity of my company. I could then put them up for sale for something I felt was reasonable given the value of my company + the value of the Bitcoins themselves. People would know that they could freely and almost anonymously resell the equity of my company without trusting anything else than what the Bitcoins represented. No need for lawyers, no need for contracts regarding selling and buying of equity, no need to meet at all to do the exchange. My company could also pay the owners dividend, because I would always know which wallets owned the special Bitcoints.

My question is therefore: Is this currently possible, given all the nice scripting features in Bitcoin. And if not, then are there currently any plans to modify Bitcoins to enable such a feature? 

Needless to say, I believe that there is a huge potential in this, because one could basically mark the owner of billions of things (virtual or not) by assigning something like 0.00000001 Bitcoins to each thing. This way one would always know who was the true owner of that specific thing.
As you say following the outputs of a transaction could be used as you describe, there are more people that like that kind of use cases and that's why ColoredCoins was created or Zerocoin which try to make it completely anonymous.

Indeed so many people is trying to add metadata to coins that in 0.9 version of the client there is a new output type that can include 80 bytes of data with no other use (you can read more about it here https://bitcoinfoundation.org/blog/?p=290)