Hello there!
We have also played the newest expansion and come up with similar issues. We have not yet reached a final decision, but there are a few possibilities:
About Burgs or Forts [Linna (=Castle) in Finnish translation]:
1) No extra protection for a meeple in the Fort. This means that it must be decided in which half of the original city the meeple is. This may be decided when a Fort is played, and it cannot be changed afterwards. The dragon and tower take the meeple when they reach the tile where the meeple is. This rule may be made even harder if the meeple is eaten whenever a dragon enters either of the tiles a Fort lies on. And the same for Towers. :
2) It would be nice to get some extra protection for a meeple hanging on top the Fort: this happens, if meeple is eaten by dragon only if dragon moves over the Fort, that is, over both tiles of the original city in two consecutive moves. Sounds confusing, but I think it might work... This might make Fort a bit different from an ordinary city, which it after all is not.
The same applies for Towers: when same Tower reaches both sides of the original city, the meeple may be eaten. This means, that Tower must be placed "under" or "over" the Fort. Otherwise it will never reach the whole Fort. This rule may be justified to fit in the Carcassonne spirit if one thinks, that a Fort is more complicated as a building than an ordinary (although a bigger) city. Then one could think that it's easirer for a follower to find a hideout inside a Fort than from a city... What do you think?
3) Total protection for the meeple in a Fort. This is easiest but perhaps the dullest option..
About Bridges: Indeed, the most powerful way to use bridges is to connect fields! Otherwise they might help you out of a bad situation, although they are not as powerful as
-Ekrates