Well, an expansionport would require ppl to be interested in one, for it to be a meaningful feature. ie, someone that is interested in making something that uses it.
The most realistic would be to make a Mega ST compatible expansionbus though.
OTOH, this board would require you to remove the CPU and fit it on the board (preferrably in a socket), and with the CPU socketed, you already got a kind of expansionbus anyway.
