Looking for areas where an open source alternative is feasible and required.If possible, explain Feasibility in terms of implementation and profitability.
I believe almost everything in the public education "stack" should be open. That would go a long way toward equalizing the opportunities available to students and staff in public schools. There is plenty of funding available for education-related products, but most of that is steered toward private companies. The quality of these products is often abysmal, particularly in the UI/ UX area and interoperability.
A free software implementation of SystemVerilog for hardware guys. Hardware development is rapidly growing and the ways to over come its complexity in verification all requires proprietary software tools.
Most of the things I can think of are firmware, like for tractors, thermostats, hearing aids, etc. Things that are generally so proprietary that it's hurting the industries.