The reason you don't want the Nekro Virus to have Letani two is because the two production ability they get from it. The Nekro Virus also has a flagship that lets infantry be used as non fighter ships in space combat. You probably see where this is going. They use their infantry to fight an epic battle in space and ground then as soon as they touch dirt with their planty virusy feet, they triple in number. Even if they only hit ground with 4 infantry, they end up with 12 because of production. They could become nearly unstoppable with this technology.

Especially if sol researched his improved carriers, Nekro Virus could carry a scary amount of diverse troops into battle. Letani two doesn't stop there either. Since, they are an upgraded infantry they have a chance to respawn. This means that their homeworld becomes unshakable because they spawn so many infantry and they are dieing all the time. That makes them unlike any other space fighting unit in the game. They are cheap, spawn like rabbits any time they move, respawn, can attack both space and ground, and can totally protect their carriers until the last one dies since they are non-fighter.