Your electrician is the one that needs to approve the design, at the end of the day although we all have put in some valuable advice, it is not appropriate for any of us to design a house re wire for you over the internet.
he/she will answer all these questions and point out wiring routes and methods with a 1hour site walk and talk.
I understand you are doing as much as you can to keep the costs down but do not underestimate the importance of getting the right design and specifications sorted early on, failures at this stage can have safety implications later that could cost a fortune to rectify.