Are you sure? Which key dose the wwan card has? I thinlk there are 4g modem cards with the B key out there (siera EM7565) which supports the usb 3 interface used by this card. But for B keys there are also sata ssd available, maybe even pcie ones with just 2 lanes. Which interface are you intend to connect to the m.2 slot anyways or do you have to provide all interface specified for a key?
Edit:
I even think wwan and gnss modules are supossed to use the b key which is also intended for ssds. Or am i mistaken that the modem should go into the m.2 slot. Because wifi is already on the chip isn’t it. Or do you want to us 2 m.2 slot a wifi and a wwan one?