So based on the recent screenshots released in this post and a couple of the FE sneak peaks, it seems that tactical battle maps will be related to the terrain being contested. If this is the case, then this is awesome and a huge improvement.
It would be even better if this had real effects on the battle field. For instance:
Sieges (hint, hint): know this wont be in FE, but next expansion maybe?
Rivers: Already in FE, it would be great if these provided choke points, maybe there are only designated places where you can ford the river, or allow the construction of bridges. Then said bridge can provide a chokepoint on the tactical map. Put a beefy guy on the bridge and pick off everyone else with archers.
Forests, swamps, etc: it would be great if types of terrain had effects and traits associated with them. Forestry traits that gave units increased initiative when in forests, swamp navigation that gave units increased tactical movement in swamp tiles, etc. A whole host of options.