I realise that it would make the game more complicated but it would be interesting if there were different research paths to follow rather than everyone following the same one.
I guess what I have in mind is something like the research paths in the Civilisation/FreeCiv series - people could choose to research a broad range or a very specialist path. So you might get someone who has researched an electronics path so they can build electric engines or something, but because they haven't researched anything on the petrochemical path, they can't make something as basic as plastic.
In Civilisation/FreeCiv, the player can not get very far along a single research path because, for example, higher military knowledge requires metallurgy developments etc - this might be a bit too complicated for Itycoon but again, it could be interesting - eg, a player is prevented researching push-button phones on the electronic path until they have researched plastic on the petrochemical path.
This sort of freedom in research would make the game more interesting as it's another choice for the player to make. It would also help stop famines and gluts in the market - at the moment, (I presume) a bulk of players are at exactly the same research level so suddenly the market is flooded with a certain good because everyone has just researched how to make it and wants to cash in.
I suspect I haven't been very clear about what I mean here - please let me know if you would like me to clarify anything 