Aggregate audio device I/O routing

Creating an aggregate audio interface in OsX is a little trick we learned pretty late on.

We have 3 interfaces running into an analogy console and lighpiping each, plus running the console software for each interface isn't a consideration as some have been dropped for ElCap onwards.

Aggregate device works beautifully with one drawback. You get a crazy high channel count as the aggregate device just shmushes every IO together, including non-functioning ADAT and SPDIF. With two 8 channel interfaces This means re-routing a lot of multi output mixes.

Is there a way of controlling for this? Is it possible to assign/route I/O channels in aggregate devices so that the channels we want to use are in a nice little ascending line of numbered outputs?