I can think of a theme you could add without having to reduce the number of territories.
There's an old fiction concept called "Pave The Earth". It's a satirical future paradise, where the important people drive gas-guzzling SUVs all day, with no other purpose but to drive; everyone else is consigned to pits, which offer up fuel for the SUV overlords and hamburgers for their drivers.
In this map - make the white areas the pits (and objective: control them all to win); the various areas (with their current colors) could be roads (blue), parking lots (beige), quarries/pavement production facilities (red), salt flats (purple), and grassy wilderness (green). The impassible borders would simply be the normal barriers one might find at the edges of these things (for instance, the quarries' borders are impassible cliffs, except for the few paths leading into each quarry area - and since each such area has only one space that can be entered, make that space the plant that makes pavement from the quarry's product; likewise, the roads only have on/off ramps at certain locations).
Yes, it's a large number of areas. That's the point: it is what's left of Earth (or, at least, a large section thereof).