Problem with making a USB 3.0 A/B/Micro adapter - detects cable as USB 2.0
Use a USB3.0 hub, it has precisely the purpose. You will save on two long cables. With wiring like yours, you will not have any performance gains since you likely use the same root hub in your host system. 

Use of passive adapters and extenders is not encouraged by USB specifications. Solder-down wire adapters are 99% doomed. Of course you can go full-blast and develop a junction box with carefully configured USB 3.0 repeater ICs (lookup Pericom or TI or else), but it will cost you a lot of efforts.