There are known biases throughout RC4 output. There are really bad biases towards the beginning. A small file would likely be XOR'd with certain bytes or patte

There are known biases throughout RC4 output. There are really bad biases towards the beginning. A small file would likely be XOR'd with certain bytes or patterns of bytes. If this is not exploitable in your hypothetical scenario, it maybe exploitable in others. I think this is generally unsafe.