Why OW not support 3\4G modems ? Same modems have up to 128mb RAM and up to 64mb ROM and have wifi, or mobile wifi routers. With OW It is much easier to customize =)
You can try to boot a mainline kernel on one and see for yourself. If you're lucky then you might have a serial console (provided you hooked one up). You will not have radio or usb support, which sort of limits the usability given that there are no ethernet ports (which would probably be unsupported as well if there were any). The usb device controller part is fixable. The radio part is fixable if you can get the chipset vendor to help you. Good luck with that.