Doom was 3d, and enemy's/items/objects were billboarded(a single plan that always faces the camera). This technique is still used in next-gen games for their speed purposes.
Strife:
What I think your looking for is a 2.5D approach to creating a game. This is actually quit simple to accomplish using a 3d backdrop and a single 'billboard' plain.
By looking at FF Tactics we can see that it uses a 3d grid based level. Navigating consist of moving across the grid with your character a certain amount of spaces per turn. To create the characters a single plain is bill-boarded and texture with the character with an alpha map.
Now to get the rotation effect you'll have to calculate the characters angle relevant to the camera's angle, and texture it accordingly.
A simple way to do this(fixed camera with angle 0):
CharacterA = Object Angle Y(1)
Select CharacterA
Case 0 : Texture Object 1,1 : EndCase `faceing away texture
Case 90 : Texture Object 1,2 : EndCase `faceing right texture
Case 180 : Texture Object 1,3 : EndCase `faceing backwards texture
Case 270 : Texture Object 1,4 : EndCase `faceing left texture
EndSelect
Now lets add an angle to the camera(intervels of 45degrees for easy of use):
CharacterA = ABS(Object Angle Y(1)-Camera Angle Y())
Select CharacterA
Case 0 : Texture Object 1,1 : EndCase `faceing away texture
Case 90 : Texture Object 1,2 : EndCase `faceing right texture
Case 180 : Texture Object 1,3 : EndCase `faceing backwards texture
Case 270 : Texture Object 1,4 : EndCase `faceing left texture
Case 45 : Texture Object 1,5 : EndCase `faceing away/right texture
Case 135 : Texture Object 1,6 : EndCase `faceing backward/right texture
Case 225 : Texture Object 1,7 : EndCase `faceing backward/left texture
Case 315 : Texture Object 1,8 : EndCase `faceing away/left texture
EndSelect
This is mostly guess work and a layout theory of creating this effect. I'll create a test object and get back to you with the resluts.
Now for the effect to look convincing you'll have to create a separate set of animated images for each angle for each movement your character takes. You could cheat and pull a Diablo, or do it by hand with some nice pixel characters.
