We introduce a research framework for the design of interactive experiences in the domain of emergent narrative, an application area of computational narrative in which stories emerge bottom-up from the behavior of autonomous characters in a simulated storyworld. Prior work in this area has largely concerned the development and tuning of the simulations themselves from which interesting stories may reliably emerge, but this approach will not necessarily improve system performance at its most crucial level---the actual interactive experience. Looking to completed experiences, namely simulation games like Dwarf Fortress and The Sims, we describe a series of shortcomings that yield interesting design challenges at the level of interaction. First, the richness of underlying simulations (and the stories that emerge from them) are often not made apparent to the player. This is because current content-authoring practice is not tailored to the simulationist concerns of emergent narrative, a problem that marks our first design challenge: that of developing new authoring techniques that will yield modular content. Moreover, a related issue is rooted in how content actually gets deployed---our second challenge is that of developing compositional representational strategies. Next, systems from which narratives emerge are typically unable to discern those narratives from the uninteresting event sequences that more commonly appear. When this happens, emergent stories may not be showcased by the system, and in turn they may go unnoticed by the player. This problem represents a nascent task area and our third challenge, story recognition. Lastly, even if a system is able to recognize some emergent story, how should it showcase it? We call this last challenge 'story support', and conceive of systems that could showcase (and support) emergent stories as they are unfolding. In this paper, we motivate and discuss each of these design challenges and, for each, summarize prior work and propose new approaches that future work might take.