Posts from Ideas and suggestions.

I suggest adding control to other fire schools:
* add movement point regeneration to water = logistics become even more valuable
* add army stack teleportation from hero to hero to fire = weak heroes can help clear areas more actively, intelligence becomes more valuable, playing with multiple heroes becomes necessary

Please provide a detailed description of the mechanics, including numbers and how it depends on the skill level.

it would be better to introduce some other limitations

Secondly, it's a very alien mechanic for Heroes... limiting teleportation by the number of hit points... it would be better to introduce some other limitations.

Regarding the first point – in this version, Water becomes stronger than Logistics in the late game; just one movement restoration spell alone justifies taking the school, and the other spells are also enhanced. Plus, the blue hat is enhanced with an additional control spell.

Regarding the second point – it's a very foreign mechanic for Heroes... limiting teleportation based on the number of hit points... it's better to introduce some other limitations.

In Heroes 5, there's a certain number of creatures per mana unit. However, this isn't the best option; instead, introducing a coefficient that depends on the level would be good.
For example:
10 creatures, level 1, for 1 mana
7 creatures, level 2, for 1 mana
4 creatures, level 3, for 1 mana
2.5 creatures, level 4, for 1 mana
1.5 creatures, level 5, for 1 mana
1 creature, level 6, for 1 mana
0.5 creatures, level 7, for 1 mana
Or, depending on the growth rate, but that might be less elegant.

The level should not be higher than 3 (because Teleport is much more useful), and not lower than 2 (so that they don't start using it on level 111).

This spell would be much more useful than Teleport, it's essentially an improved version of Teleport, and it's quite overpowered, so a minimum level of 5 is necessary.

If you're creating a spell for exchanging troops, it makes the most sense to base it on Teleport as the most similar spell.

For example, the base version could exchange with the nearest hero, the advanced version with any hero, and the expert version could reduce the mana cost.

Variations could include exchanging with a hero/castle/both.

In principle, a range limit wouldn't look too out of place (similar to Visions).

The level should be no higher than 3 (because Teleport is much more useful) and no lower than 2 (so that players don't start exploiting it at level 1).

A range limit... I don't know... It's a very strong restriction. It's better to make the mana cost/number of troops more expensive.
The base-advanced version doesn't look very good either; again, a stronger restriction on the number of troops looks more harmonious, in my opinion.

The Teleport spell is probably better because you can transfer artifacts (for example, the Book of Earth), and another hero can use the Teleport spell after clearing something. The troop teleportation spell can only be used when building in a guild (which is quite random). Therefore, level 3 is fine.

They can't even agree on basic things compared to your latest posts (say, changing some useless skills), and here you are suggesting some fantastic ideas. First, it's all too far from the spirit of the game, and second... you can argue about it endlessly. It's not the most difficult thing in the game to get up to 1000 mana + water expert... You banned the hat bug, you should be ashamed....