I managed to get hand on a second hand Kensington SD4700p USB-C 3.0 Docking Station (at a reasonable price). This device offers USB-C and USB3 ports and other bells and whistles (like gigabit ethernet, HDMI & DisplayPort ports). This is not the kind of device to bring on the move (it requires a specific power supply), but at home, this unit can be of valuable interest. This one resolves in some way my issue with my 2014 MBP Retina...
I'm also trying to replace the internal HD of a MacBook Pro Unibody (Mid 2012) with a Seagate SSHD ST500LM000 and the SSHS fails to be recognized by the MacBook Pro. Placing the SSHD in an external enclosure is working perfectly. According to the previous comment, this might be related to the internal SATA cable and I would be pleased to learn the exact reference of a replacing item for this SATA cable. Many thanks in advance.