In most RPGs, you have to select one of start Heroes. I have an idea to make difference between them not only in stats and skills. They can have additional features (like passive abilities available starting from level 1 with no skillpoints spent, but not displayed on command panel because there are only 2 free buttons (or 1, if they have Attribute Bonus with Hide Button - No)). For example:
Mage can restore his mana, just holding position for some time and not doing anything (and not being attacked). (Effect works at the same time as Shadowmeld, but during daytime too.)
Druid can eat flowers (placed on entire map), restoring his health with time, although the others have to bring the flowers to special NPCs to craft healing potions.
Assassin increases his/her movement speed while moving long distances.
Warrior, quite the reverse, can run with increased speed if ordered to move somewhere twice (or with Ctrl held, or any other way to order that without a special button on the panel), but the ability has cooldown (also displayed in any available way).
Archer increases his/her attack range with each level gained.
One more idea (but probably unreal to come true) is items that affect the Hero based on his/her level - for example, an item that increases your Strength by your level. (Note that maximal Hero level on my maps is usually 100) As I know, upgrades do not affect the abilities of items .
Mage can restore his mana, just holding position for some time and not doing anything (and not being attacked). (Effect works at the same time as Shadowmeld, but during daytime too.)
Druid can eat flowers (placed on entire map), restoring his health with time, although the others have to bring the flowers to special NPCs to craft healing potions.
Assassin increases his/her movement speed while moving long distances.
Warrior, quite the reverse, can run with increased speed if ordered to move somewhere twice (or with Ctrl held, or any other way to order that without a special button on the panel), but the ability has cooldown (also displayed in any available way).
Archer increases his/her attack range with each level gained.
One more idea (but probably unreal to come true) is items that affect the Hero based on his/her level - for example, an item that increases your Strength by your level. (Note that maximal Hero level on my maps is usually 100) As I know, upgrades do not affect the abilities of items .