Though he has the ablitiy to kill G4 and FG2, they both work for Chronus and the Zoalords wouldn't like having their valuable guyvers killed off, plus if he goes after sho all he has to do is say help to agito and G2 is facing Zeus or any other of sho friends like Max
Yup, sad fact him is that he is outpowered and out numbered by his enemies. However if were ever to become a warrior guyver he could give Chronos the middle finger and do his own thing, even then he would have some powerful people to fight.