As you suggest, with the current download cacher, the -o switch is probably your best bet (though this is an area we are exploring to provide more granular options).
One way you might generate the file containing the desired download links is to leverage Session Relevance within either the Console or Web Reports. The basis for this is described by @jgo in: Identify what web sites all the fixlets need access to?
The following session relevance will return all the download links from BES Support:
unique values of ((matches (case insensitive regex “((mailto:|(news|(ht|f)tp(s?))://){1}\S+)”) of matches (case insensitive regex “^(download|prefetch|download now|download now as|add prefetch item).*$”) of scripts of actions whose (exists script of it) of it) as string) of fixlets whose (fixlet flag of it or task flag of it or baseline flag of it) of bes sites whose (display name of it = “BES Support”)
This can be filtered in any number of ways based on the metadata associated with a Fixlet, but for instance, the following will return the download links from BES Support where the source release date is within the last year:
unique values of ((matches (case insensitive regex “((mailto:|(news|(ht|f)tp(s?))://){1}\S+)”) of matches (case insensitive regex “^(download|prefetch|download now|download now as|add prefetch item).*$”) of scripts of actions whose (exists script of it) of it) as string) of fixlets whose ((fixlet flag of it or task flag of it or baseline flag of it) AND (exists source release date of it) AND source release date of it > (current date - (1 * year))) of bes sites whose (display name of it = “BES Support”)