What reason would that be?

It is inefficient to do "cardio" (cardiovascular training for the explicit purpose of increasing general endurance) using only two large muscle groups (glutes and quadriceps). If your intention is to do cardio you can achieve the same level of effort in less time with running, which uses your entire leg and some upper body, or rowing, which has the benefit of not destroying your knees in the process. That said, 250 bodyweight squats is definitely achievable in one year for anyone of normal health, so my estimate of your probability of success is dominated by your willpower and desire to stick to that particular goal.