Slaves are the cornerstone of the strategy. Without it the strategy cannot be performed. A pop at 0% happiness will not produce anything, if you enslave that pop it might still be unhappy but you will get a standard yield out of it. This is the prerequisite for getting anything out of your early game conquests. As you really don't have the time and resources to wait 10 years before happiness is back up to a level where you will be able to make use of them.
Personally, I'd like a fuel system similar to other 4x space games (including Distant Worlds). So that rushers indeed don't snowball that quickly and the rest of the galaxy has time to react.
Isn't fuel already modelled in fleet upkeep? Maybe it would be enough if the upkeep costs scale with distance from the next spaceport.
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