Have you played with bbp_parse_args() yet? This is used ~100 times in bbPress to allow you to change array arguments ‘before’ or ‘after’.
BuddyPress introduced bp_parse_args in BuddyPress 2.0, and as they have some good docs and we don’t yet here for bbPress check this out:
https://codex.buddypress.org/plugindev/using-bp_parse_args-to-filter-buddypress-template-loops/
So for the bbPress function bbp_list_replies() you’d use bbp_before_list_replies_parse_args
https://bbpress.trac.wordpress.org/browser/tags/2.5.4/includes/replies/functions.php#L2192
Does this get you on the right track? I hope so as I’ve never played with custom walkers 😉
