Hmm... I'm not so sure if Splash Lagoon could be the park's only log flume? It's basically the same as River Rafts at Chessington (same manufacturer). The capacity isn't high and it is great for the younger ones.
I'd say if another Log Flume style ride is needed, it needs to be more substantial and creative in it's layout. Something along the lines of Viking Voyage, Valhalla, Chiapas or Stormforce 10 is probably what I'd have in mind for what the park would benefit from as a water ride.
A rapids could work in the same scenario but I'd worry about it being tamer due to Health and Safety.
I definitely agree with the Teacups, I'd say it needs replacing more than anything. With the park working with Mack nowadays, I'd say bringing in one of their classic teacups or a Twist N Splash could be a upgrade to the one they have now.
Pirate Ship, I'd love to see it upgraded into a larger model and the one they have now being kept as the junior version.
Kontiki and Viking Boats (and also to an extent Pirate Ship) are all rides that would easily be integrated into the Viking area if relocated. I'd say Vikings or Pirates would've been the natural theme for that area they are in now.