Seems to me that you are looking to take on lots of needlessly troublesome and costly problems in order to chase a trivial improvement in efficiency. It is not likely to provide a favorable cost vs. benefit situation. The efficiency losses associated with the increased operating problems will probably exceed the efficiency gains that you are seeking. You really don't want to be dealing with needless fuel leakage problems.
Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.