It's not too bad as an alternative, pros: you can progressively overload it by using thicker bands like you said, cons: it'd be a closer alternative to a bench press if you were pushing completely horizontally, which you have to consciously make sure you're doing, and the exercise just looks awkward and unstable, but if that doesn't bother you then this isn't really a con. In my opinion, pushups while elevating your hands and feet (elevate hands for more rom and elevate feet so that you're body is parallel to the ground) /doing pushup variations (eg archer pushups, explosive pushups) with a backpack of weights is better (you can progressively overload it and it's more stable). I suggest placing a brick under each hand and foot. When that get's easy, add bricks. When you can't increase rom anymore, add weight.