Did this ever get resolved? Same issue here.
It's frustrating, I'm trying to move away from Google and have gone with Fastmail but the choice is:
Fastmail app - only shows one notification (get new mail, the notification overwrites the previous one) but actions appear fine on Pebble
Aquamail - shows multiple notifications, but actions never appear on Pebble (even if the notification is for only one email)
Maildroid - actions work on Pebble but only "reply all" appears on the notification shade on the phone, and for some inexplicable reason they don't have "reply" (reply-all is bad practice)
Argh! The temptation to just go back to letting Google spy on everything.
Incidentally Aquamail is the only one so far that isn't doing the Pebble actions

The behaviour seems to be the same whether Android Wear support is turned on or off, it's like it has no effect.