well for my purposes i think the CAAN tile and composite would be similar, just on different scales...
but let me talk this out here;
a CAAN is a combined air-armour-naval formation (with a few mechs I think and at the RCT/brigade-level, correct?) and so we can assume artillery as well...that could get messy and crowded fast. I google-search yielded no universal "Composite" symbol. I should think maybe a circle, so an anchor in a circle?
what would you use for a marine expeditionary unit? maybe that would fit better? on that note how about units with amphibious capabilities? I saw an LVT tile in my search, but that just was a box with "LVT"
as for the composite unit...i think of the kind of thing found in the Mekong back in vietnam, a smaller CAAN almost; infantry, armed landing craft, floating fire support, airmobile assets.
I did not notice a landing craft code for any of the naval assets either.