As for BSDI, is it possible for them to trade their /17 in to ARIN for a more likely routable one?
NO. Arin can't presume to know what is or is not routable.
registries have no control over backbone BGP filters, they can't guarantee routability. If there's not a good chance of their allocations being routable, then what's the point in allocating space?
Lets back up a tad and approch from another direction. Routable by whom? One of the important (and some would say the most important) things a registry can do is keep accurate information on delegations. If a user of space does not care that its packets are visable via Sprint (to pick on an ISP at random), then why should a registry care, as long as the user of IP space is happy. The registry should be willing and able to make such a delegation and registry clients ought to be able to ensure that the registry has accurate data about them and their delegation. IMHO, registries must be blind to ISP routing policy. --bill