Not exactly sure what you are asking, so let me state what I think I am hearing and you can correct me…
1. You want to use a different WiFi card. But not one that uses USB.
2. Since the BT card is integrated with the Airport Express card it means you'll lose BT if you get a different WiFi card.
3. Because of #2 you are trying to find a different BT device so you can keep BT.
My fuzziness is with #2 and I cannot help you with #1.
However, I can most certainly help with #3. I've been using Belkin BT 2.0 USB adapters for a few years. They work natively with no driver installation and brought BT 2.0 to a G3 and a G4.
On my Quad I DO have the BT card and Airport Extreme, but there's still enough interference with the BT card to cause mouse jumpiness and lag so I went back to using my Belkin adapter.
Both the internal device and my adapter are active but the adapter overrides the internal (which is what I want).
Just got another two over Christmas on eBay. You can get one for $11. It's USB, but it will work off one of your keyboards USB ports (I have mine plugged into the left side). It's convenient and keeps the adapter out of the way while making for a very short distance between the adapter and my Magic Mouse.
Here's the eBay auction for it
MODS, NOT MY AUCTION!
https://www.ebay.com/itm/BELKIN-Bluetooth-v2-0-USB-Adapter-Dongle-for-Notebook/400071266977?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
Belkin F8T013 (I use the F8T012 which is 100m range, the F8T013 is 10m).