Virtual reality exposure therapy (VRET) is a promising approach in treating phobias such as fear of heights (acrophobia). VRET provides an effective, cost-efficient, scalable and individually adaptable alternative to traditional exposure therapy. To further foster the potential of VRET, a novel concept called Playful User-generated Treatment (PUT) was derived from expert interviews and literature review. In this paper, we provide additional insights regarding the applicability of PUT in real therapy scenarios. For that purpose, practicing psychotherapists (n=13) participated in an online survey and shared their assessments regarding PUT. By conducting qualitative content analysis (inductive category formation), we identified opportunities and challenges that should be considered for the design of playful VRET systems. Opportunities were seen for preparatory habituation, increased control and self-efficacy, improved interaction, economic usage and a realistic display of anxiety-inducing environments. Challenges included lack of direct communication and realism as well as pseudo-habituation to virtual environments.