Of course God could have created us "with the gospel already in our heads." God can do whatever He wants to.
And he chose to transmit his inerrant word using imperfect languages and the writings of sheepherders, collected over millenia, edited and reinterpreted by thousands. Seems reasonable, especially for a being that can do
whatever he wants to.
God could have written the Bible Himself, but instead God chose to do things differently, having humans participate in His plan.
Your dictionary must have an interesting definition for the word "participate." If the Christian God exists and his plan is what we understand it to be, then I'd hardly call humans participants. At best, we're rats, dropped in a maze and made to hunt after a piece of supernatural cheese.
The same can be said about everything else, sin, good works, poverty, pain, suffering, sickness, death, etc. Why didn't God just create everything and everybody perfect?
Good question... do you know the answer? Oh, and "works in mysterious ways" doesn't cut it.
The message of the Bible has not been changed, as you claim, and that to us Christians is more evidence that the Bible is the word of God.
First of all, I didn't claim that it hasn't been changed - I claimed that it could have, and you wouldn't necessarily know. Difficult as this concept may be for you to understand, it's important that you at least try to:
Words have meaning. Now, with that said, it's ridiculous to say that the message of the Bible hasn't been change. For crying out loud, Christians can't even agree on
what exactly, constitutes the Bible. The Bible of Protestants is very different than the Bible of Catholics, which, in turn is very different from the Bible of Orthodox Christians.
Just one example is the "The Great Isaiah scroll", which was found in the Dead Sea Caves in 1947. It is dated at about 100 BCE and is the oldest copy of Isaiah known to exist. Previously, the Codex Leningrad, dated at 1,000 AD, was the oldest known copy of the Hebrew Bible (including the book of Isaiah) in existence. The Great Isaiah scroll is 1,100 years older than the Codex Leningrad and gives us the opportunity to compare the Biblical text over the centuries.
I'm by no means a Biblical expert, but at least according to Wikipedia, your representation doesn't seem quite accurate. Selected quote from the wiki, referring to the Dead Sea Scrolls: "
copies of some Biblical books found at Qumran reveal sharp divergences from the [Masoretic Text]."
This copy of Isaiah contains many minor differences from the later Masoretic text (the text which forms the basis of the modern Hebrew bible). Most of the differences are simply grammatical (for example, spelling certain words with an extra letter that does not alter the pronunciation). Of the remainder, for example some added words, most do not significantly alter the meaning of the passage.
And yet, according to Michael Barber, the copies of the Dead Sea Scrolls reveal sharp divergences from the Masoretic Text...
That's pretty impressive compared to any other ancient text, secular or religious, for which we have any remaining copies.
A significant number of ancient Greek texts, quite accurate and
completely unchanged, are available to us today. Is that evidence of Zeus?
You are the one who brought up J.R.R. Tolkien in this discussion. Tolkien understood literary studies, history and linguistics much better than you and I do, and he had no problems accepting that the Bible is the inerrant Word of God no matter the form in which it was given to us.
I brought up J.R.R. Tolkien and this means that I must accept every position that Tolkien had? That's some crazy logic right there. Besides, appeals to authority are logical fallacies, and logical fallacies don't fly with me

Tolkien's personal beliefs are of no concern to me.