Understanding the ||w|| = 1 constraint for SVMs
The constraint is interesting in itself as it prevent divergences (or other strange behavior) for the optimisation problem that is the calibration process. The value it is set to not that much. $||w|| = 1$ is a practical convention. For $||w||$ to be constrained to 2.53 you would have need to :

Have some practical interest for it to being set to 2.53, which there is none. $||w|| = 1$ might help simplify some theoretical calculations.
Reach a consensus between users that it would be good to use this value. It's not hard to see why the consensus was reached for 1 instead of 2.53.