You cannot plug a bluetooth dongle into a USB hub to make the hub wireless
I can see the logic in what you are trying to do: Mac has bluetooth, so by plugging in a bluetooth dongle into a powered hub, that hub can be accessed by bluetooth. Seems sensible on the face of it.
However, the bluetooth dongle doesn't work that way. It needs something to tell it what to do. An operating system will provide an interface to the dongle so that you can say "I want to pair with this device" or "I want to send audio to that bluetooth speaker". The USB hub can't tell the bluetooth dongle what to do.
You can buy 'wireless' USB hubs
There are hubs out there which can be set up to act the way you want to. Grabbing an example product (discontinued):
The WiRanger® is the world’s first wireless USB 2.0 Hub combining Icron’s patented ExtremeUSB® technology and the industry standard 802.11g radio to deliver cable-free USB around the home or office.
The WiRanger wireless USB 2.0 hub is a four-port hub and dongle set that will enable immediate high-speed wireless connectivity with maximum reach extending beyond 30m.
Searching for wireless USB hub returns plenty of results, but hardware recommendations are beyond the scope of this site.
But consider speed
One last thing is that by going wireless you will almost certainly have a lower throughput than a wired solution. For keyboards and mice this may not be a problem, but since you mentioned a flash reader specifically, I thought I'd give you a heads-up. Reading large amounts of data from a flash card (eg photos) will probably be significantly slower.