Must agree that I liked some elements of CtP, but by no means all of them!
1) Stacked combat was a big plus in my opinion, and is what I'd like to see in civ4. Even if you don't have a seperate screen like CtP, it should be possible to conduct combat at 'stack level', with some very basic 'maneuvers' thrown in. One good way of doing things would be the 'Birth of Federation' approach, where you could choose to go to the tactical combat screen, or simply allow the computer to resolve the battle for you!
2) Trade Routes: Oh YES!! For pirates to actually be useful, this would be a great addition to the game! However, pirating trade routes should NOT be automatic, as it would make it much too easy. This is where CtP got it wrong, IMHO!
3) Public Works: Definitely would like to see this in Civ4. However, I think that workers should be in the game too. My idea is that workers would be 'immobile', but attached to a particular city. The number of workers you assign to a 'terraforming' project would determine how quickly it got done. The PW budget would determine how many jobs you could do (as each task would have a given cost). Under this system, any unused workers could be allocated to any PW project outside its borders. Also, there would still be a chance for an enemy to 'capture' your workers and make them into slaves!
Personally, I could do without the whole lawyer and corporate unit, as well as the cleric and evangalist unit. Not only did they look silly, but many of their functions could have been done through a more abstract system!
Yours,
Aussie_Lurker.