What does that mean for the Loch Maiden game, well with an already strong theme this means I should be tying the complexity where it exists to the theme as tightly as possible. There are still good reasons to simplify and hone the actual mechanics, but sometimes leaving in a piece of thematic complexity can help and embellish the gameplay.
Perhaps a good example of this is the trait deck. The game as it is sitting now would run happily enough without traits (positive and negative cards that apply things like razor claws or boils to your monster). One of the narrative elements of the game is seeing your monster grow longer and having traits brings extra roleplay opportunities to your character and offer other attributes to that growth that differentiate the monsters. This definitely adds complexity, but it is logical thematic complexity and thus sits very well.
The mood mechanics also add complexity but with their strong tie-in to how the game flows and the theme with the maiden being the focus they should feel logical and approachable.
Monster sketch direct from the Galaxy Note 8 Sketchbook Pro app (via dropbox)