You fight generic First, Second, and Third class SOLDIERS all throughout the game, starting in midgar, contuining at Junon, and then finally you encounter first class soldiers in the raid on Midgar.

Fact of the matter is, SeeDs were weak unless equipped with GFs, in which case you could consider them to be super humans. However, unequip the GFs, they are still SeeDs, just very weak ones who wouldnt be able to do much.

Soldiers, by definition, are modified. You can't "unmodify" them, because that would mean they arent soldiers anymore, just normal people. Soldiers without that modification arent SOLDIER at all.

Thus, if you ARE a SOLDIER, you are automatically genetically enhanced- SeeD is not necessarily so, remove the GF and they are nothing.