I would let the MARKET choose a replacement. The gov, for years has made (and continues to make) bad choices as to who(m) the winners will be.
Car makers could easily adjust their cars intake/injection and computers to run on less "enhanced fuel". Methanol could be a choice (my dragster runs on it, and it has less noxious exhaust, runs cooler and cleaner, etc), especially since CO and CO2 are prime ingredients, and if what you say is true about CO2, what better way to recycle that in to Methanol. Alternatively, there are hundreds of compounds that could replace it. Were the gov NOT on the side of big oil, alternative fuels could have been compounded since this first reared it's head in the 1970's, instead of waiting in line and now being beholden to a part of the world that would not hesitate to celebrate our demise.
Not a rant, just an opinion to not fall over for the wants of the gov, especially when it is not in OUR interest to do so.
I didn't say anything about CO2.
Most of what you suggest would never be accepted by the MARKET because of COST. But unless you know about enthalpy/entropy of reaction and other aspects of the 1st and 2nd laws of thermodyamics, you might not understand why. But I can tell you that the market will not accept $6-$10/gallon gasoline, and that's what your suggestions would likely require. So the market already has had a large say in the option that was selected.
Injection and computers will not take us any further - believe me, that's already been done and has taken us as far as we're going to go with current fuels and compression ratios. There are a lot of technical tradeoffs to consider, and you don't seem to realize that with your post.
I challenge you to list a dozen of the "hundreds of compounds" that could replace ethanol, and then estimate their COST so that the MARKET can decide.
And we are becoming far more energy independent with natural gas - a large part of the reason that gas prices have been decreasing the last several months. I'm not so crazy about the environmental aspects of fracking, but the government has stayed out of the way of that a is letting the MARKET decide.