Saw this post and it seems to be exactly the setup I am going for. I was debating getting the Mayflash Wireless PS3 Controller To PC USB Adapter which works with 4 controllers in D-Input mode but only 1 controller in X-Input mode. Supposedly the pressure sensitive buttons work on it as well although it isn't clear if it is limited to one mode or the other.
The other route I am considering is as you described, using a dedicated bluetooth adapter along with ScpToolkit. I already have an Orico BTA-403 (CSR 8510A10 chipset) that works great with my 8BitDo controllers but my understanding is I can't use another bluetooth of the same chipset especially when using ScpToolkit because otherwise both bluetooth devices will become unusable in Windows. Which means I will have to find another brand/chipset bluetooth adapter solely for ScpToolkit that won't conflict with my current CSR 8510A10 adapter.
So my question is, which bluetooth devices are you using for your PS3 controllers/ScpToolkit, 8BitDo controllers and does using ScpToolkit allow pressure sensitive buttons to work?