So, I've continued to chew on the concept of an amphibious assault scenario in the back of my head. Here is a mock-up of how I'm thinking I would lay such a scenario out:
The amphibious landing assets would deploy into Zone A, the supporting fleet into Zone B. The defending player would deploy their land units in the inland zone (still working out where exactly) and would also have defensive emplacements of some kind on the beach. Initially, the defending player would have no naval assets on the table; on turn 2 or 3 these would enter via the two Zone C's to try and disrupt the landing effort.
Only the landing craft, medium, and small Naval models would be allowed to enter the Shallow Water zone, and I'm contemplating the Beach Zone either slowing movement or making units that are in that area easier to hit. The two inland objectives are intended to be reachable by the invasion force within 4-5 turns.
I've drawn up the above diagram to use a 4x6 table using the short edges. The Cigar mat might work, though it is geared to use the long edges:
http://cigarboxbattlestore.bigcartel.com/product/beachhead-4x6-plus-160That could be paired with other mats to get the right geometry, I suppose!