I would absolutely love to see Geomancer as a new job, especially as a healer (a different role would also be ok, but I just like healer the most).

Ever since it appeared in SB, I wanted to become one. I like the earth/wind/water and eastern theme of it so much.

But I don't think its spells would change with the area you're in, it would be to much to program I suppose.
I always thought it could rather "create" surroundings with its spells. They could have large ground effects (like Asylum, Salted Earth and so on). And also effects surrounding the caster or a target, and they could work similar to the Bard songs, that you need to be in a certain distance to the effect for it to affect you, but it's mobile and not stuck in place.
Different elements have different effects of course. They could also give them some more eastern themed actions and things that have to do with real geomancy.

That CNJ already has earth/wind/water doesn't make Geomancer impossible, because RDM also has elemental spells. Also WHM almost only has light aspected (even though they call it unaspected) attack spells anymore, so who cares if Geomancer shares the same elemental spells below a certain level.