I'm almost sure that i have at least one silver coin left somewhere, that may or may not have been from castle(1990-1993) Better get through my stash, and see if i can post some pic. of it...
As much as a small cannon would be extremely usefull in the pirates theme, i don't think it could cross over into other themes, and unless you want a small gun, that is able to fire, you can easily moc one with few bricks.
I would say, as previsiously stated, that we need schienic-painted wall-pieces, especialy the ones with timber framing, as seen on the old black nights castle from the beginning of the 90's. This would be usefull, both for castle, town and pirate.
Bring back "ye olde compass" from the 90's pirate ships, oh please!
I also vote strongly for painted tricorners, and maybe more colours than brown and black (did they release reddish-brown in the new sets?!)
These would only go for pirates theme, but i don't think it'd be harder to pull off tgan the shakos(shacos?!)
It would also be very easy to remold some of the hat ornaments/feathers from castle. Also quite usefull for diversity.
As said before, and as allways a reappearing problem in lego, there are never enough female figs.
And i think it too would be nice with more beards in different models and colours...