Rapid SaaS Project Management Web App Development

I am in the process of launching a new startup. I require a skilled and experienced developer to quickly and cost-effectively build a proof of concept SaaS web app.

Key Features:
- Collaborative Workspace: The app should facilitate seamless team collaboration by providing a shared workspace for tasks, files, and communication like Figma
- Visual Sequence Diagram Creation: A drag and drop interface for creating visual sequence diagrams, with a library of reusable components, and real-time collaboration capabilities. Sequences should be numbered by step, Participants should be easy to add from a pre-populated list, and Interactions from Participant to participant to remain the same size after text is inputted.
- Navigation Panel: Easy navigation to various sections of the app like Notion
- Embedding Capability: The ability to embed content from external sources like Whimsical
- Scope and Dependency Visualization: The visualization of numbered scope and dependencies per Participant from the sequence diagrams to enhance project management. Potentially bulleted lists auto-generated from the created sequence diagrams.

Ideal Skills and Experience:
- Proven track record in designing and developing software systems.
- Strong background in building SaaS web applications.
- Familiarity with task assignment, tracking, and project management.
- Proficiency in implementing real-time collaboration features.
- Experience in visual sequence diagram creation tools.
- Ability to rapidly develop a web app proof of concept within a limited budget and time frame.

If you have the skills and experience in these areas, I would love to hear from you. Please provide examples of similar projects you've worked on, and an estimate of the time and cost required for this project.