I took up maintaining GladiusEx, which shows friendly cooldowns. It currently uses cast-time spec detection, but I'm fairly sure there's a way to do better.
On the wotlk version of PartyAbilityBars, I had written a nasty hack that'd keep a list of players it needs to inspect, and would use a InspectFrame in the background to trigger inspects. Upon receiving INSPECT_TALENT_READY, I'd then try to detect talents on the current unit (...that I had kept in a global value...).
I definitely think "There has to be a better way!", so if someone has a trick, I'd like to know it :). Ty