Excellent analysis.
Its really quite cheap to rent cards to get to max CP.
I have a lot of spare CP on accounts that I never have time to play and I'd like to offer more cards for rent but its a very time consuming and tedious process.
I wish there was a way to automate it.
Thank you @apshamilton! You can find someone who you can trust and the person would the job for you and then if the cards are rented the person earn some percentage.