Two suggestions regarding buffing a couple of otherwise mediocre-at-best spells. The mod would be fine without implementing them, but I think they'd open up player options at least slightly, without unbalancing anything.
First, give Mistforms summoned via Shadow III the Marksman promotion (if possible make it so that barb ones do *not* spawn with it). There really isn't much of a point to them at the moment; as temporary summons with only two moves, it's hard to imagine a scenario where you can really exploit their HN and invisibility to wreak havoc without your opponent immediately determining that you are the culprit, spotting your Shadow III Archmage, and declaring war- at which point you probably would have been better off just sticking to Air Elementals for harassment. With marksman they'll fulfill a special niche that no other summon currently does, allowing you to pick off the weakest combatants in your enemy's stacks without the need to resort to expensive Assassins. Plus they give the Eloheim a way to get marksman units without having to tech all the way to the end of the tree or capture the city of someone who can.
Second, have Spirit III give all discipline units in the caster's stack the Homeland promotion. We all know that Spirit III is utterly useless at the moment, in both MP and SP. Since Discipline units right now are the only line which cannot benefit from an exclusive arcane boosting spell, I figure Spirit III can be amended to kill two birds with one stone. Granted, +10% strength within your own borders and +10% retreat isn't particularly impressive, but at least it gives them something. Maybe both the cultural defense and retreat odds boosts should be increased to 20% or something.
First, give Mistforms summoned via Shadow III the Marksman promotion (if possible make it so that barb ones do *not* spawn with it). There really isn't much of a point to them at the moment; as temporary summons with only two moves, it's hard to imagine a scenario where you can really exploit their HN and invisibility to wreak havoc without your opponent immediately determining that you are the culprit, spotting your Shadow III Archmage, and declaring war- at which point you probably would have been better off just sticking to Air Elementals for harassment. With marksman they'll fulfill a special niche that no other summon currently does, allowing you to pick off the weakest combatants in your enemy's stacks without the need to resort to expensive Assassins. Plus they give the Eloheim a way to get marksman units without having to tech all the way to the end of the tree or capture the city of someone who can.
Second, have Spirit III give all discipline units in the caster's stack the Homeland promotion. We all know that Spirit III is utterly useless at the moment, in both MP and SP. Since Discipline units right now are the only line which cannot benefit from an exclusive arcane boosting spell, I figure Spirit III can be amended to kill two birds with one stone. Granted, +10% strength within your own borders and +10% retreat isn't particularly impressive, but at least it gives them something. Maybe both the cultural defense and retreat odds boosts should be increased to 20% or something.

What if the boost was permanent? It's strange how it's so much worse than Enchanted Blade.
Earth Elementals are great stack defenders and hit like freight trains, Air Elementals have insane range and are one of the very few ways to deal with stuff like the flying Mercurian chariot UU or Manticores. Air Elementals should be fixed though so they actually spawn Lightening Elementals like their description says.