If SEC will not let him create his own coin he will end up picking the coin where he can be a whale and promote it just like what he is doing right now with Doge, I believe he will not satisfy with Doge, and he will add more coins to his portfolio, he is looking for a good coin to promote his reputation is at stake here, Doge is not a bad start but he should choose a coin that is much better than Doge.
Why would Elon Musk needs the permission of SEC if he wants to create his own coin. There are thousands of coins that are created and many projects that collected over billions of dollars and no project developers took any permission from any authorities even though i think that the projects that collected money will be audited in the future. If Elon releases a coin and never collects money as seed fund then there is nothing to worry from the SEC.
If Elon releases a coin that is beneficial for the market it will be a success and considering his influence in the financial market anything he does turns to gold.