I propose the following...
First off, at the beginning of the game players start with 5 tiles (or so) and begin by placing them in turn, just to get the cave system going. Then the game would move into the next phase where everyone places their pawn somewhere (in particular) to begin exploring.
Turns consist of the following, in an order to be determined...
* Playing a tile
* Moving your pawn
* Searching the tile you're in
* Dealing with an Existing obstacle or Encounter
Playing a Tile:
Players choose a tile from [their hand/pool of tiles/at random from stock] and place it anywhere that it connects to the (total) cave systlem. Points are scored for completing Caverns, Rock Fixtures, or passages. Note: The placement does not have to continue a passageway, it just has to match on all sides- rock to rock, cavern to cavern, and passage to passage.
Moving Your Pawn: Useing an Action Point system- pawns can be moved around the board at the cost of APs. Moving is important because it gets you to a more lucrative place to search, and it allows you to get to the exit.
Searching the Tile You're On:
By spending APs a player can search the tile they are on, thereby drawing a card. The type of tile dictates which draw deck to draw from.
Dealing with Existing Obstacles:
At the cost of APs, and with bonuses for having the right equipment, compare the total to the difficulty of the obstacle. Follow directions on the card for winning or losing that comparison.
