From the Ptolemaic preview it looks to me like the South-Eastern African provinces will be useful as they will probably contain all those interesting numidian axemen units that the Egyptians want. However they're probably quite difficult to take for the same reason.
Lets not forget that this is not the same all conquoring Egypt with the super-killer-pharoh's-terminators and infinite wealth (though Im sure theyre still gonna be pretty rich) of Vanilla RTW.
For all we know Ptolomeic Egypt may in fact be weak and underpowered in EB, and will need to take those Ethiopian provinces just to survive.
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