You don't actually need an ASN to get PI though? You can use PI just fine with BYOIP. Actually... I don't think you are even required to announce them on the Internet.
One common scenario is two links to the same ISP, so everyone knows which link is active (you can do active-active (load balancing/sharing), or change weights or local preference for active-passive):
* https://learn.nsrc.org/bgp/two_links_one_isp_backup
* https://learn.nsrc.org/bgp/two_links_one_isp_load_balancing