To Gaussian Solutions' question: We want the system to make the process of paying for the trip as easy as is technically possible. Your raise payment standards: We would not prescribe a standard, but would look to see that your development plan is based on an understanding of how payments are, or could be handled, and makes clear how easy your system can make the users' question of, "how do I pay for the trip?"

adding on top of the above question: "do you expect the solution to handle the payment for the trip as well? or is it enough to provide the cost for the trip? If the expectation is that the solution handles payments, do you have any standards that the payment system should handle, or is their a preferred payment system on which the proof of concept should be demonstrated?"

As a Concept of Operations phase, phase 1 doesn't require a functional payment system. Your suggested approach of a feasibility assessment and design is more in line with the expectations at this phase