I realize my options are limited due to my hardware choices, but I have a question: I have a 2014 5K iMac, and a new 15" tbMBP. I'd like to explore the option of using the MBP as my desktop machine with a 5K monitor. Rather than go out and buy one, at least, for a trial period, I'd like to use my existing 5K iMac for this purpose. Does anyone know of a way to 'plug and play' my MBP on the iMac display? I bought a Thunderbolt cable and tried to make a Thunderbolt Bridge work, but success eluded me. Thanks in advance for any suggestions.