I didn't look into Truestate Plus yet, but reading your post I guess I can use it for my camera state ?
Like :
- Behaviour layer. Where I put stuff like zoom, views type, follow, based on player's actions
- Effect layer. Where a can trigger shaking, shaders and other fun stuff based on player's reaction to danger or player's condition (is poisonned, low life, full power mode, etc)
Am I right ?