I am looking for an RF chip that offers a set of bit-rates similar to the PHY bit-rates used in IEEE 802.11 (144 Mbps-900Mbps in 2.4/5GHz bands). I want to embed it on board with a processor with my own firmware. I wish to write my own MAC layer. 

To be clear, I went to be able to write a simple program that selects a modulation, frequency and tx power, then loads a raw payload (based on some logic) and transmit. On the receiver end, similarly, there is a program to set a certain modulation/frequency and begin listening. An interrupt is fired at the beginning of receiving a frame. 
I have been looking everywhere on Digikey, RF Components, Mouser etc. but I do not see any chip that has a clear indication in its datasheet that it allows raw tx/rx. Any idea of any chip that does that?

This is a common feature in IoT chips like AT86RF215. There are 31 different 802.15.4 modulations including OFDM. But I am struggling to find a chip that shows explicitly in datasheet how a specific modulation is selected like the IoT AT86RF215 chip. 

I know this can be done with SDR in a USRP. But I am looking for an existing off-the-shelf module.