I have some random thoughts about the battle royale scenario described above.
The importance of porc in the middle is, first of all, somewhat regulated by having to get to that middle in the first place.
If the middle contains very little resources, then opting to porc there early costs you resources in comparison with choosing to temporarily build economy instead. But of course unless your enemies are diligent enough, nothing prevents you from doing both.
Map-based reclaim sources become much more important because the units that allow exploitation of those are typically mobile.
Athena becomes the choice factory if it can be teched up, being mobile and compared to losing your 800m factory to the Outside, with no chance to reclaim.
Razors suck at defending against ground units. If the porc mid strategy is made sufficiently comparatively expensive in relation to expanding, other types of statics could be plainly tacnuked (or outright nuked!).
The middle could be further made hard to defend (and to own quietly) by giving everyone free LOS of it.
It's possible to make the square middle of the map unbuildable. This prevents the porc scenario inside it, but still allows porc camps or area-controlling Cerberi right outside the limit.
Capturable or rezzable static energy sources could be very interesting to provide temporary overdrive options. Same with geothermals.
Storage is going to be interesting. Perhaps such a map should allow mobile storage units to be built.
Using a deathwall instead of lava allows water units to still exist on the map.