Hi. I am trying to study the flowchart you attached on my Linux machine using LibreOffice - but it is not displaying correctly. If you have time, would you mind re-attaching the flowchart in PDF format? (It might help other bidders as well.)
Tentatively, I could devote 15-20 hours a week to this. I have both a Raspberry Pi (version 1) and an Arduino Uno for testing / development.
One of the main hurdles for me (or any other bidder) would be replicating your hardware setup - with touch screen, weight sensor, beam sensor, credit card machine, etc.. I may be able to partially absorb the costs for some of the items (if, for example, the touch screen was useful in other projects), but would need exact part numbers to check costs and availability.
I am based in Ireland.