Does it have to be phones? What about other electronic or even non-electronic devices?
For electronic devices I prefer some challenge but not too hard. I was able to refurbish iPhone 5 almost perfectly, went unnoticed at Genius Bar on several occasions (not that they checked against modifications that closely back then) so it became too easy for me, just like laptops.
On the other hand some devices are just impossible to repair perfectly, you can't get a lot of the perishable parts so reassembly will always be a messy job, example: older Surface devices that did not have any repairability considerations.
In my opinions water-resistant iPhones are the best for me. I was able to reliably disassembly, restore and test OK water resistance feature for iPhone 7 through X, not that easy but certainly achievable.