Go to your ..settler2datamissions directory there are several rtx files. Mis_0000.rtx - Mis_0009.rtx are the campaign missions. Edit them with your favourite txt editor.
Now I could have written a ten page manual about how to do this, but I'm just too lazy, so here goes:
In the first section of commands (beginning with !Set_Commands=Player1 or alike (depending on version) for player 1 and the same for player 2 and so on.) In som missions you are player 1 and in some you are player 0. However, you are always the player the list begin with.
There is a long list looking like this:
!Add_People= 0 #
!Add_People= 1 #
Etc
The !Add_People= 26 # offset shows the number of generals in your HQ. Set # to whatever number you want between 0 and 250.
Of course you can experiment by raising another !Add_People offset number. 29 for instance means "Pack Donkey". You can also add wares in the !Add_Ware list. Placing houses is also possible in that list, but that requires coordinates to work.
That's all I guess. Remember to change file formats back to rtx if you renamed them.
NOTE: Editing these files doesn't modify your savegames. It only changes the starting stats of the missions.
All chapters
In your savegame directory (i.e. ..settler2save)
there is a file called mission.dat. Read it with your favourite txt editor.
Now change all the 0:s in the top line to 1:s.
Abracadabra! All chapters playable!
NOTE: If you changed the file format to txt or whatever, dont forget to change back to dat or the game won't launch.
Change speed, Get entire map etc.
While in the game, type in THUNDER. Don't mind the windows popping up. A exclamation mark should appear in the upper right corner.
Now,
Press F7 to get the entire map
Hold Alt and pres 1-6 to radically change the speed.
Also, you will be able to see name and productivity of enemy buildings.
NOTE: In the Gold edition THUNDER is replaced by WINTER.