I find this is a bit difficult to envision. After all, we are a long ways from 2178, and we have already discovered and collected antimatter. Do you have any theories on potential new fuel types?
Without significant improvements in the ability to store antimatter, it isn't very useful as a fuel as it tends to only survive in our universe for a few fractions of a second. Moreover, you'd still eventually run out of your supply of antimatter, and since in any real system you'll require more energy to produce antimatter than you'll get out of the antimatter when using it as a fuel it would be impractical to have the ship fuel itself with an onboard antimatter production plant, unless it happens to take long stops at natural energy sources which can be used to power the antimatter generator.
Also, I would take some issue with "discovered and collected antimatter" - the situation is more that we've been able to artificially create antimatter after theorizing that such can exist, and we can keep it from destructively recombining with matter for short amounts of time. Since the process of creating antimatter consumes more energy than is released when the antimatter recombines with matter, it isn't a way to generate a perpetual motion machine, either, especially once you start to consider that in addition to the efficiency in the antimatter generation process you also need to consider the efficiency in the energy capture process during the matter-antimatter reaction, and that even though the matter-antimatter reaction is releasing lots of energy, it isn't necessarily releasing useful energy.
That being said, I'm not particularly unhappy with the way ship ranges are implemented in GCII. The only thing that I really wish were added would be some way of extending the range of ships so that I don't absolutely have to have X life support units on every ship in any given fleet. Does it make sense that I can put a ship out in space for decades without it ever even needing to pass within sensor range of a planet or a space station? Not particularly. On the other hand, most of the games that I've played which include a mechanic that forces you to bring ships back to supply points every so often are either too gentle about it (in which case the mechanic doesn't exist, for all intents and purposes) or too harsh (in which case the mechanic becomes an impediment to gameplay). In my opinion, Sword of the Stars did a good job of it, Distant Worlds and Starsector do an okay to poor job of it (especially Distant Worlds - relying on the computer to properly allocate resources usually works out, but it can be one hell of a problem when the computer's idea of what to prioritize doesn't match up with what you think should be a priority, and you don't really have a good way to influence those priorities), depending on what's going on in the game, and Sword of the Stars II as launched did a very poor job of it, which has since improved somewhat (still, having to return to port after more or less every battle isn't exactly conducive to my enjoyment of the game), but other people's views will differ, and that is one of the problems of balancing out this sort of system, because my opinion of where something becomes an impediment to gameplay is probably different from your opinion of the same, and it could be radically different.
I also tend to agree with jmontesi4 about the range-boosting effects of starbases - at some point, the amount of supplies required for the vessel carrying the supplies out to wherever the stuff is being sent should begin to exceed the value of actually getting the stuff there, especially if the supply vessels carry a live crew; using an automated vessel could potentially greatly extend the range, but you still need to get the personnel for the ships and stations out there in the first place, and it needs to be something that can be done within a reasonable time-frame given that at least some of the members of the starship or starbase crews have lives outside of their present jobs that they might want to return to at some point, and presumably there will always be some supplies which are in one way or another perishable. I don't necessarily agree that there's much point in adding it to the game given that in GCII we could make trade ships with speeds in the double digits and the maps weren't terribly large (on the order of a thousand light-years on edge, or ~260 parsecs on a side) with relatively high speeds relative to the scale of the map (up to about eight and a half thousand times the speed of light, or about 50 parsecs per week), if you really wanted to push ship speeds. More practically we might be looking at top-of-the-line ship speeds in the mid-teens to mid-twenties of parsecs per week, which should neveertheless allow for reasonably short travel times crossing the map.
