Just kicking around this concept in comparison with DF.
OK, so Dungeon Fantasy has a few traits that make it particularly adaptable to an RPG boxset. As I understand them, they are:
- The implied setting is well known, and can be left out/ignored.
- The implied scenario is as straight forward as kill monsters, steal the treasure, grow more powerful. Other goals can be handled by an ambitious GM (Rescue X, Recover Y, Kill Z, etc.)
- Because of the scenario, characters are mostly one-dimensional combat monsters, but have easily differentiable combat abilities.
- Characters are understood to be slotted into a particular role, which helps with niche protection and templates (i.e. there are no generalists.)
- There is a wide variety of opposition, that can plausibly be reused, because is a short enough distance away for the PCs to hike/ride to.
Now let’s do these for space opera:
- Space opera is dominated by a few very different interpretations. Also, unlike the generic "olden times" of DF, technology can differ between the settings (consider the debate about technologically enhanced characters in space opera.) Also, particular events of scenarios tend to depend on the setting.
- The number of scenarios in space opera is no less than 3. Combat is a possibility, but not an inevitability (well, at least per session). Growing in wealth may not happen either (see Military Sci-Fi).
- The differences in scenarios means you can’t have one dimensional combat monsters as your default. Also, combat abilities may not be terribly different, especially because of guns (not necessarily bad, unless scenario is combat heavy.)
- Generalists are a fairly common sight in Space Opera, which makes it hard to enforce templates and niche protection.
- Opposition can be just as wide as it is in Dungeon Fantasy. However, it tends to very planet to planet, unless it is or was moved by a starfaring race.