Found myself with an unexpectedly empty Special Day on Dissidia, so I've been spending my time running Squall and Firion through the Duel Colloseum. The +3 AP growth has had a remarkable effect, as has the 2x Exp growth, letting them both shoot up heavily in levels, and also master a lot of their abilities. Sadly, Squall still has no Brave -> HP moves, but he's making up for this with a fairly remarkable array of HP moves, and Firion just has a lot of Brave->HPs I've managed to unlock, and even afford. Of course, since he only recently got Weaponmaster, and I'm still learning to use it, that still leaves him a sad, sad, panda in mid-air.
Squall gets no Brave -> HP Attacks. His moves do link up in such a way that you can make custom combos with them (at least, supposedly they do now; Japanese Squall sucked cause he was suppose to be able to do this, but couldn't! Well, that, and he lacked stuff like AERIAL ROUGH DIVIDE), and he's more about tearing apart the person's brave, raising his own, and then killing the guy in a single shot anyway.
Brave -> HP attacks available in this game are...
WoL: Several moves, forget offhand; one leads to Bitter End, the other leads to Runeblade.
Firion: All his Ground Brave moves but Sword Slash can link into Double Trouble; note that the only difference between A, B and C is what move they use as a base (probably done that way so you don't master Double Trouble with Reel Axe, then have it mastered for the other 2 moves as well.)
Onion Knight: All his damn moves eventually get Brave -> HP links. Some will require mastering the Brave -> Brave links though.
Cecil: Nothing. Like Squall, though, he can create custom combos (Search Light is a big one for Paladin Form, for example)
Bartz: Holy can chain into Flare (Onion Knight's version, not Terra's; requires specifying cause he uses Terra's Holy, and Terra technically uses Flare in Holy Combo <_<) once mastered; don't think he gets anything else otherwise.
Terra: Holy Combo once mastered can chain into Ultima.
Cloud: I think Sonic Edge chains into Finishing Touch, and his basic Aerial Brave move chains into Omnislash Ver. 5.
Squall: Covered.
Zidane: 2 of his aerial moves chain into Meo-twister. He use to have more, but free energy became a normal HP attack instead, so yeah (actually...the moves Free Energy chained from use Meo Twister now, and Meo Twister's old HP Chains don't exist anymore! Yes, its weird, guess Free Energy just works easier as a standard HP Attack than Meeo Twister does.)
Tidus: ONe of his moves chains into Quick Hit or something; honestly don't knmow with him, cause like Zidane, one of his Brave -> HP chains became a stand alone HP attack, while the other did not.
None of the villains have Brave -> HP Chains, outside of Golbez, who gets Cosmic Ray on one of his attacks, but can't remember what. Shantotto and Gabranth don't get any either. Jecht does have a quirk that allows him to use HP Attacks in the middle of Brave combos if you get the timing down right, but that's not quite the same.