Reading between the lines, it looks like you want to hear: "This is impossible. Go to your boss and tell him it can't be done."

But back on topic. Perhaps you should ignore the fact that you may ever want to upgrade.
Just try to speed it up as much as possible and keep track of your modifications. At the end, you can choose a couple of optimisations that cover 80% of the speed increase and apply the same techniques on possible upgrades.