Adding 3 dimensions to a 2D roguelike

[xibalba]

http://www.gamefaqs.com/boards/19667...reams/61975735

Azure Dreams is a proprietary game for the PlayStation 1. It's a 3D roguelike, with elements of townbuilding sims, dating sims, and monster raising and fighting games. The game uses 3D graphics to represent the terrain of each floor in the Monster Tower (which is the tower you must climb in the game, just like you have to descend into a dungeon in other roguelikes), but the actual player character and non-player characters are 2D sprites. Items and effect animations are 2D sprites as well.

I'm no programmer, so I'm wondering; how hard is it to add a z-axis and 3D graphics for terrain to an existing 2D ascii roguelike? It doesn't have to be a fully functional z-axis (in that you can have a something on a floor above you, at the same x and y co-ordinates), but it would instead allow you to have hills and ravines to traverse on the current floor, which would change battle mechanics.

The battle mechanics in question:
*Height Variance = Damage Variance.
//Attack from above, and you deal more damage. Attack from below, and you deal less damage.
*Line Of Sight
//Ranged weapons and spells which use LOS can be blocked when there is something between the actor and the target.
*Arcing
//Weapons like bows - but not crossbows - and some spells activate along an arc. As such, they can be fired over an obstacle, but not around it to either side. Depending on the position of the obstacle relative to the actor and the target, the obstacle may block the attack.
*Knockback
//Some attacks can knock a target back one square. If the target falls from a higher square to a lower square, the target may suffer fall damage.
*Fall Damage
//Fall Damage increases the greater the distance you fall.