Arahants, Bodhisattvas, and Buddhas by bhikkhu Bodhihttp://www.accesstoinsight.org/lib/auth ... ttvas.html
I don't fully agree with bhikkhu Bodhi, but I find that he has some interesting points. On the arahants and buddhas, I have this simile:
Before Issac Newton found out that F=ma no one knew it. After he found out F=ma, he taught that to everyone. What he taught is the most important thing. He went through many mistakes to find out that formula. Now the way is already opened, no need to reinvent the wheel.
IMO, the bodhisattva is exactly like that. Yes, there is a way to become the Buddha similar to there is a way to become Issac Newton, or someone the first in something, simply because it is a historical fact.
And after found out the truth, no way the Buddha would teach about the bodhisattva way, it is similar to in no way Issac Newton would teach others to follow all of his experiments and mistakes, just to know F=ma.
E.g Issac Newton maybe tried F=ma/2 or F=mv, etc.. and then found out all of those are false. Finally, he would simply teach that F=ma, because only it is worth to mention. Like that, the Buddha only teaches about suffering and how to end it, he would never teach about the bodhisattva way. That's why no one can find the teachings about the bodhisattva way in the Nikaya.
So my conclusion is that, there is a bodhisattva way, but no way it is a clear way like someone can point out in suttas, it is just random walking. The Buddha, like Issac Newton or every inventor, tried many way before the invention, when he had not found the eightfold path. Some lives, he practiced and taught the way to devas world, some lives he tried the way to brahma world. Some lives he was maybe a Christian, a atheist, who knows? He just tried his best in every situations out there, sought all guides and advice available at the moment. And still, all of that is inferior to the final teaching after he got enlightenment like every beta version is inferior to the final formula F=ma.
All the teaching claimed from Buddha's mouth about the bodhisattva way are false, the bodhisattva way is the hidden way because of the reasons above. If you like that way, let yourself be prepared, you need much more than the official false guides from the suttas (coz there isn't any).