This is interesting and pretty analogous to the story of Macbeth.
If you destroy the power center(the Constitution) to usurp power, you will never sustain it.
To understand this we need to go back to 1949, when India was called Dominion of India. Only after the Constitution was adopted did we officially become Republic of India. Now what if we shred the Constitution? Two things -
i. Republic of India or the definition of India that we know currently will cease to exist automatically.
ii. Something will have to take its place, also the nation (not the state) can be named as Republic of India but that would just be semantics. So yes form a legal point of view - the Constitution is everything. And going against it is treason. Period.
So what if some other Constitution takes its place?
That would be a revolutionary change - a new state will be born, but the legal continuity or more appropriately the transition of the Republic of India to Islami jamhuriat or Martian republic etc will be questionable to say the least.