Oh crap!!!! I meant DO
2-in-1 opening?

Yes and no.
No, because after 1.d4 Nf6 2.c4, you have to choose one of them, can't do both.
Yes, because the pawn sac ...b5 cxb5 a6 is also a theme in many KI positions where black has played ...c5.

Those are more like the benoni though. is the ...c5 KID more or less respectable than the modern benoni?

Wait...What if white didn't move the c and d pawns? Would it still be a good idea to continue with the Benko Gambit or just do another opening with Nf3?

Just play d5 and pretend you're white with c5 since no pressure would be on your center. That's why they play ...Nf6 usually as a first move of any indian defense since it always wants to be there being part of all the setups so why not play it first? I think it's good to change the setup and just take the center if you can.
Does the King's Indian and Benko Gambit go together well?