Here's your setup. Why 4 ... a6 since the bishop is already blocked from b5?
My novelty set-up the Lenear Variation

Here's your setup. Why 4 ... a6 since the bishop is already blocked from b5?
Thank you!

3...c5 makes it more of a Sniper. It used to be considered a variation of the Modern, but now it is recognized more as a defense with independent significance.
I'm on my phone and trying to bring up the diagram with it is a hassle but my inspiration for the idea is the Benko Gambit to sac the b-pawn or the St George in lines the pawn can be won back.
1.e4/g6 2.d4/Bg7 3.Nf3/c5 4.c4/a6!?