I'm afraid I can't think of a clever way to achieve what you want at present.
However, yesterday we announced BMC Discovery version 11.2. It's not quite GA yet, but should be available in the next couple of days. In amongst the big new features, there is a small search enhancement that does let you do what you want. You will be able to do this:
search flags (include_destroyed) Host
with (traverse Host:HostedSoftware:AggregateSoftware:BusinessApplicationInstance as bai where not destroyed(#))
where name = 'plmulti-w01b' show name, os_type, so_version, os_arch, vendor,
#InferredElement:Inference:Associate:DiscoveryAccess.endpoint as 'Scanned via', last_update_success,
#bai.name as 'Name'
Duncan, thank you for the response!