Quote from Jack
We're currently not sure how to push heroes in terms of customizability. One idea is to have a spell tree, so there are multiple spell 1's to choose from, etc. However, this increases the amount of spells massively, and makes it harder to balance everything. We also don't have a good way to integrate that into the UI without being clunky (see sotis for clunky UI). Having hero specific items is certainly one way to add to heroes, but keep in mind that you can already upgrade attack, defence, hitpoints, and mana. If items are merely doing the same thing but cheaper after a certain stage, then items wouldn't add to the game at all.
Personally, I would stick with some kind of item base. It keeps the game balanced and leaves strategy. My reasoning, is that there is a limit to how much you can upgrade and in what direction. Allowing the purchase of direct stats, would cause issues in people creating a glass cannon and destroying some opponents of lesser skill.
Some ideas that have floated around before: Limitation and Mastery spell system: You can level your spells however you want, but you can 'specialize' in one, giving it an altered effect than it would normally have.
Either/Or abilities, you can choose a skill, but then you cannot have the other. This was intended as a hero type in E.P.I.C. and had a lot of interesting concepts behind it.
If you would still like to pursue the tree option, you could. Though if you did, I would definitely recommend that you can only level up when you go to heal then so that newer players wouldn't want to upgrade in the middle of a fight and lose horribly. That, or have it so you set up how you want to build your hero before you start playing or something.
In the end, personally, items only exist to limit somebody from say leveling up straight hp and unable to die or the alternative, somebody leveling straight attack and killing everything without trouble. Items make this only possible in leaps and bounds, not a linear rate, as well as the fact that you have a limitation to how many times you can get the same upgrade before you have to pay an excessive amount for the next. Kind of get where I am coming from?
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Something I just thought of when I saw the terrain picture, you aren't seriously sticking with the 3 cannons/pylon/capture point... Are you? Why not make it all one building, just when you destroy it, the building goes into a 'neutral' state until it is uncontested and captured? Just sayin'.
None.