I guess the biggest audience here is for medieval / dungeon style.
Give that a tile can only have one level, the next big problem in creating a multi-level shootout is that (traditionally) tilesets use slopes to connect different levels of elevation. So, for example, if you have two peaks at level 2, they are separated by five tiles (2>1, 1>0, 0-0, 0>1, 1>2), which may be a problem for visibility and weapon range.
This can be improved by the use of doors. Transitions within area are almost instantaneous. Some tilesets allow doors in elevation walls; also, you can place doors such as the CEP ladder door anywhere, using the AdjustLocation trick. In our example, this reduces the separation between level 2 peaks to three tiles (1, 0, 1).
It seems that the same thing can be done using walkmesh steps that rise almost vertically. The only example I can think of offhand are the watchtowers in CEP Rural Winter etc where the player climbs a near-vertical ladder from level 0 to level 1. Perhaps one of our tile makers can comment on whether it's possible to climb more than one level vertically within the same tile.