Where there is a will there is a way they say. There was a discussion on a Facebook page about loading 10ga shells with a 12ga Lee Load-All. I suppose it can be considered clever but I think it would be better to save up your money and get a single stage MEC. For those who are curious as to how it's done here is the link to a Youtube video on it.
https://www.youtube.com/watch?v=z6HEO9GxgQM