I'll probably see about buying an old one. But I've also been brain-playing with some kind of mount that'd keep the thing to a roughly uniform thickness-- say, having a guide mounted parallel to the blade, so keep the depth of cut roughly uniform. Thing is, such a guard'd run cross-wide to the motion of the saw.
And, given the size of the boards I'm thinking of, I'm wondering if there's some way of running the blade horizontally-- letting the board rest flat on a work surface, and have the blade run back and forth, like a horizontally-mounted jigsaw. Interesting problem...