Might as well start thinking about this now. Obviously no game can be balance perfectly, so some amount of thought is always going to be how it could be done better. I think there are three Areas we should consider:
Meta Balance
Things completely outside of gameplay that aren't balanced, such as maps (Flags on Exile are not the same) or starting Positions (Is the 4th player spawn on cataract too far from the shop?). "Exile isn't balance because Dark has an easy MPS flag, while light has an easy HPS flag."
External Balance
These are the balancing mechanisms once a game has started, between players. For instance, a certain Demigod vs another, or perhaps a certain Skill that one player has, compared to a different skill someone else has. "Spit is too strong, as it kills other Demigod's Well."
Internal Balance
These are mechanisms that each player has, and generally dictate what play styles work or don't. "Nobody ever uses Yeti's with Sedna because they are too weak." This kind of balance isn't something that makes a player win or lose against another, but rather just limits which strategies/actions are good enough.
For the purpose of the discussion, let us consider only a few things at a time if possible. A list of all the changes 'you would personally make' to something can be entertaining to consider, but we will likely get places, and come to better agreements, if we can cite actual reasoning, and discuss that. Here's an example:
Bad Example
Blade of the serpent is too good, I never use the staff of the warmage, staff should increase attack speed by 100%.
Good Example
Favor Item: Blade of the Serpent
What is the balance issue? The Blade allows for significantly better mana generation than other favor items, making it at the very least, not internally balanced. Compared to the Staff of the Warmage, it gives more damage, and 300 less mana. However, with a single activation of the Blade, and dealing 400 damage in 10 seconds, you get that back.
What kind of Solution? I think we should fix this balance problem by making the Staff of the Warmage Stronger
Proposed Solution: Allow the Staff of the Warmage to be activated to give a large attack speed boost for a short time.
This gives us three points to discus. First, do we agree the balance problem exists? Second, after we agree it does, what kind of solution do we want to do? (For instance, you could have also just made the Blade weaker, instead of making something else stronger, or even removed it if the concept is simply unbalanceable or too negative to play). Thirdly, what roughly should the fix be? I strongly urge you to leave out numbers. It is easy to negatively react to a large sounding boost to Damage, when that isn't really the point, the point is that it should give SOME amount of boost. Disagreeing over the exact numbers is a minor thing we do after all else is done, and is generally experimental in nature.
If at all possible, let's try to avoid too much bickering, and focusing just on good discussion for now. Once we can actually get the modding done, and have people willing to try it out, I think we will be able to make good progress!