1 Like being able to target squares in Tac combat (1 to x number for effect).
2 Target more then one individual in the strat map.
3 Create a separate pool of hit points for a target to act as a sheild.
4 Have effects that are persistant and move with a target if tagged (like a shield effect on a caster).
1) Have you tried the Any target type? This allows you to target any tile whether it contains a enemy unit or not.
2) This is possible to a very limited extent. You can use AdjustArmyStat as the attribute for a unit mod type to effect the stats of an entire army. The only down side here is that the unit is bearer of the modifier and takes it will him when he leaves.
3) You can actually something similar by having a spell that adjusts the base HP of a unit so that they have more HP to burn in general.
4) I am not exactly sure what you mean here. All modifiers are applied directly to the target unit and are kept on them until either dispelled or the unit is killed. A good start point for more army based spells would be again the adjustarmystat attribute.