Ill be doing a tutorial on this at some point soon. To put you out of your misery, you cant create conflicting Sciences, only Upgrades and Weapons.
If it helps, the original Generals logic was actually a clever way of allowing the player to switch factions after starting the game, so if you had chosen to play as USA (the parent faction) you could switch to USATankCommand (a sub faction) by choosing that General.
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