I’m not an expert in the Bible, but I don’t think it really ascribes omnipotency to God. I think it’s better to understand it as God being able to do all that can be done. So He may have limitations, but they are such that no other being can do something that He is unable to do.

From that sense, He is not able to save humanity freely, but he can set forth a process through which He can achieve this goal with some cost. I.e., He can create a divine being (that is either Himself in whole, Himself in part, or a direct descendant of Himself depending on your interpretation) that is able to spread His message and display an act of extreme self-sacrifice.

I don’t really understand exactly what the sacrifice did or what needed to be fixed, but I do think the stories make a lot more sense if you accept that God has some limitations. For instance, I assume that Noah’s flood was his first attempt to fix the problem (by killing everybody except for the most righteous of His creation), but it failed because He can’t do everything and doesn’t know everything. And the story of Jesus was His next attempt to sort things out.

But that’s just me thinking about them as fictional stories that really need to be edited rather than a divine and infallible truth.