I think it would make sense to take origin AS (ISP) into consideration when generating the node list for an object, that is, to make sure that not too many pieces end up within the same AS.
An AS/ISP is a potential single point of failure on the Internet. If too many pieces are stored within one and the same AS and it goes offline, the pieces will be unavailable until the problem is resolved. A typical AS consists of thousands of customers spread out over many (hundreds or thousands /24’s). If even a low percentage of the customers start a storage node, there will be hundreds of /24 candidates within even a small/medium sized AS. If/when there is a central routing problem, there is a risk of losing access to an entire object. The data will typically not be gone, but at least be unavailable for a while…