Right. We're doing this, huh?
Fuel working or not is besides the point. The question is, rather, what for? What purpose does fuel serve?
Speaking of fuel as I usually do, as an addition to the current game, I think the answer is clear. To introduce, and balance against current ship-building mechanics, the influence of infrastructure and resource production, on day-to-day ship operations and combat.
Creating a fuel-like mechanic from the power system, I really don't see the answer. It may work, but it's not expanding on the game, just swapping one thing out for another. If you rather want to play a game with a fuel mechanic instead of a power mechanic, be my guest, but that has nothing to do with putting fuel in the current game.