@Picard: The Roland Boutique range can only be powered via AA batteries or USB, so a powered USB hub with MIDI would be better than using batteries when you don't have it hooked to a computer.
Even some other synths like the Bass Station 2 allow for USB power and midi, so a powered USB connection like this would be cool for connecting a larger 61 key controller to it. Like the AKAI MPK series which is either USB midi/power or din midi with a barrel jack, but not both at the same time.
It is safe to say that there will be many more uses for this with a USB in and a USB out than I can personally think of! You may even be able to hook a CV pal to this with a USB out!
I third better mounting holes. If you are going to make a case, be sure to add those!