It was WiFi sync that was removed from AS and WMDC center for later versions. This was directed at syncing to the desktop, but since AS and WMDC created the path through which you could access your network, it effectively eliminated the WiFi passthrough feature.
You can sync and pass-through to the net via BT.
There are BT 'routers/access points' just as there are WiFi routers/access points. They are just not all that common. (
http://www.mobiletechreview.com/tips/belkin_AP.htm) You can do pretty much what you can do with a WiFi AP/Router.
What you gain with WiFi over BT is speed, at the expense of battery use.
For a small wireless network, I would still use WiFi, getting a Linksys or similar AP/Router/Switch to service the majority of items you mentioned, and get the BT AP for the handheld stuff if you are still looking to go that way. I think you will find it more economical and get better performance out of the desktops using WiFi.