It is XOR-ed with the first block to mask any pattern there, so a sequence is enough unless you think that the first blocks XOR-ed with a sequence might result

It is XOR-ed with the first block to mask any pattern there, so a sequence is enough unless you think that the first blocks XOR-ed with a sequence might result in repeats, if for example they also contained a sequence. One obvious option that might work (I'm not a cryptography researcher, so ignore me) is that you could encrypt the sequenced IV to get a secure psuedo-random block.