I think the E16 only supports grid style topologies as it doesn't have the *MESHROUTE registers feature.
The Parallella only provides north and south eLink extension and there are only 16 possible row addresses for the E16 version. So you can't put more than 16 boards in a line, and there is no way to go sideways. With a daughter board like the one shown above, if the boards arrange the chips in a column you could have three of them plus the Parallella.
Alternatively for a bit more cost you could arrange the four epiphanies in a row rather than a column. Then you would have to provide north south connectors for each of them if you want free reigning communications. Plus some way of attaching the ordinary Parallella to one of the connections. You could get 15 * 4 + 1 chips in such an arrangement. A big power supply and board feeds needed too, doubt you could feed that much current through the Parallella board! The Parallella would only be able to directly talk to one column of chips
Tim