I don't know that you can do what you are proposing, but what you can do is program additional fobs. The electronics within the fob are pretty small once you get rid of the physical key and all the plastic, so if you could get extra fobs cheap enough to make it worthwhile, you could program them, remove the circuit board electronics from the 3 fobs and put 3 electronic sets within a small box and use that as a "universal" fob. If you are handy with a soldering iron, you could probably connect them all to a single battery within the enclosure to keep the size small. It could probably fit in a box of similar size to a standard keyfob.