Conclusion:
I think my plan only really works for the sake of maximum science, not gold.
Sorry, should have done these calculations before asking the question..
Calculations:
(I use 2 from center for easier numbers, don't think it matters much)
Lets assume 10% corruption
All grassland (8 bonus grass) with nuke.
Size 21
20 (mine) 20(rail) 8(bonus grass) 2(center) =50 base shields, 45 after corruption.
45 (nuke) 22.5(factory) 22.5(robotic plant) = 135 shields total!
=33 gold without economics
=67 gold with economics.
+2 from 1 specialist
69 gold in total. 9 upkeep for nuke/factory/robotic plant =60 gold
Now lets irrigate it all: Size 41
8 (bonus grass) 2(center) = 10 base shields, 9 after corruption.
9(nuke) 4.5(factory) 4.5(robotic plant) = 27 shields total!
=6 gold without economics
=13 gold with economics.
+42 from 21 specialist.
=55 gold in total. 9 upkeep =46 gold
All grassland (8 bonus grass) without nuke.
Size 21
20 (mine) 20(rail) 8(bonus grass) 2(center) =50 base shields, 45 after corruption.
22.5(hover) 22.5(factory) 22.5(robotic plant) = 112 shields total!
=28 gold without economics
=56 gold with economics.
+2 from 1 specialist
58 gold in total. 6 upkeep for factory/robotic plant =52 gold
Now lets irrigate it all: Size 41
8 (bonus grass) 2(center) = 10 base shields, 9 after corruption.
4.5(hover) 4.5(factory) 4.5(robotic plant) = 22 shields total!
=5 gold without economics
=11 gold with economics.
+42 from 21 specialist.
=53 gold in total. 6 upkeep =47 gold
All Plains with nuke.
11 irrigated tiles and 9 mined tiles. Size 21
20(land) 9(mine) 9(rail) 2(center) = 40 base shields, 36 after corruption.
36(nuke) 18(factory) 18(robotic plant) = 108 shields total!
=27 gold without economics.
=54 gold with economics.
+2 from 1 specialist.
56 gold in total. 9 upkeep. =47 gold.
All irrigated: Size 30
20(land) 2(center) = 22 base shields, 19 after corruption.
19(nuke) 9.5(factory) 9.5(robotic plant) = 57 shields total!
=14 gold without economics.
=28 gold with economics.
+20 from 10 specialist.
48 gold in total. 9 upkeep. =39 gold.
All Plains without nuke.
11 irrigated tiles and 9 mined tiles. Size 21
20(land) 9(mine) 9(rail) 2(center) = 40 base shields, 36 after corruption.
18(hover) 18(factory) 18(robotic plant) = 90 shields total!
=22 gold without economics.
=45 gold with economics.
+2 from 1 specialist.
47 gold in total. 6 upkeep. =41 gold.
All irrigated: Size 30
20(land) 2(center) = 22 base shields, 19 after corruption.
9.5(hover) 9.5(factory) 9.5(robotic plant) = 47 shields total!
=11 gold without economics.
=23 gold with economics.
+20 from 10 specialist.
43 gold in total. 6 upkeep. =37 gold.