Your Feature Request / Idea
Make upgradeable buildings. Could be contracts. Could be research. EG: Level 1 building is vanilla with two upgrade slots, but 4 upgrade options. Level 2 building has all four upgrades applied, PLUS those same 2 upgrade slots, and same upgrade options. Level two building costs vanilla PLUS 75% (100k to 175k). 2 level 3 power plants would equal 3 vanilla ones.
Make upgradeable buildings. Could be contracts. Could be research. EG: Level 1 building is vanilla with two upgrade slots, but 4 upgrade options. Level 2 building has all four upgrades applied, PLUS those same 2 upgrade slots, and same upgrade options. Level two building costs vanilla PLUS 75% (100k to 175k). 2 level 3 power plants would equal 3 vanilla ones.