So I've been thinking about the multi-sector storm more. Using 5 tiles, we need a central tile that could be used both in any centralized part of a storm, or as a single sector storm. Then, we need 4 tiles that would go on the top, left, botton and right of this central tile. These side tiles wouldn't take up the whole sector, and would be designed so that they were modular. You could have a storm like this:
^
X>
Or like this:
^^
XX>
And it would look good.
(each character is 1 sector)