Freelancing platforms, such as Upwork and Fiverr, have become a viable source of work for millions of freelancers worldwide. However, these gig economy systems are not typically designed in ways that centre workers' preferences and wellbeing. In this paper, we describe the development and evaluation of 'Freelance Grow,' a design fiction portraying a freelancing platform that prioritises freelancers' professional development and peer support. The design fiction was informed by a systematic literature assessment, using recommendations from twenty-six sources for improving online freelancers' experiences. We then used the design fiction in focus groups with 23 online freelancers to investigate their views on the ideas suggested in our design fiction. Based upon a thematic analysis of the focus group transcripts, we present three opportunities and considerations for designing systems that further enable freelancers' work autonomy, entrepreneurial development, and peer support. Ultimately, we contribute an expanded understanding of design approaches to support online freelancers in the gig economy.CCS Concepts: • Human-centered computing → Empirical studies in HCI; Empirical studies in collaborative and social computing.