Firstly, there's nothing extraordinary about what Akash does. An SRBM is not very different from an aerodynamic target, only the target is really small. Even Barak does the same. You consider it "extraordinary" because you are ignorant about this.
Secondly, our BMD is meant for far more dangerous BMs, like MRBMs and borderline IRBMs, which are hypersonic. Akash, MRSAM and XRSAM have nothing to do here, and any BMD capabilities these missiles possess are against theater missiles and other types of SRBMs.
Thirdly, we are not like the Russians and Americans, who are capable of combining air defence and BMD into a single unit, like the S-400 and AEGIS. All other countries have independent systems with different roles, which is actually easier and cheaper to design, and you get more effective capability with a single role design. So we are following the Patriot + THAAD route, not the S-400/500 route.