I've just added a dvd writer to my 3 passports (2TB) to my BDP1.
Don't want the 3,5 drives, since they tend to make more spinning noise than their 2,5 counterparts. Most of the 3,5's use their own power adapter , which possibly introduces electric noise we don't need. Bus powered 2,5 drives obviously live form the BDP which is optimal.
Although i didn't have problems with the 3 drives, powered from the BDP1 on itself, I've now also tested a usb powered hub for the dvd writer. All drives are attached to it, and they've never been faster. Effortless and flawless.
All i can say is: no worries, buy the USB hub, add all to it and enjoy. Ive even added a 4th drive, but havent really tested it yet, thought the first impressions seem fine.
As an extra point of care, Chris pointed out you should also powerdown the hub when powering down the BDP. Ive got them on the same power switch, so thats taken care of automatically.
Library size is an entirely different aspect though, given the BDP1's limited memory and processing power compared to the BDP2. The BDP1 does it all, and takes more time when the library grows. But, the Bryston DB should be turned off, album art won't work without issues with larger libraries (30-60Kplus), or not at all, confusing the BDP/MM to the point of not working at all ....
Cheers,
Marius