Sub-Band Extraction Techniques for Complex (I/Q) Signal
I wanted to ask what are the techniques which can be used to extract this sub-band data?

That's a description of a filter bank.
Yes, the FFT can be used for such applications. You'll find that OFDM, which powers DVB-T, 4G/5G, WiFi, … (basically all high-speed wireless terrestrial links) does exactly that.
You'll also find that if you find the inherent sinc-shape of subcarriers in an FFT filterbank insufficient, but still need regularly spaced channels, polyphase filterbanks are the way to go.