Which chips are those? Most of those solutions I had seen were not actually a single output stage but rather each band had dedicated pins that went out to dedicated PA's in many cases. So wifi/BT has its own antenna and front end etc.. same for the other bands..
The combo chip itself probably has multiple SDRs internally so that e.g. you can use GPS and WiFi/BT simultaneously, but they can be connected externally to the same antenna through a diplexer.
