I like your idea, may I suggest a change for the assassin?

-Critguy (This guy focusing around getting critical strikes, and may also get armor lowering traits, basically lots of traits to increase random damage).

-Skillguy (This guy gets lots of different attack skills, like double strike, you may also make an in-combat teleport ability for him to make him more interesting).
 - Sidenote, if you need help with these ideas, I am happy to give suggestions, although I am not touching the XML... it is terrible ^.^

Just a thought anyhow, depends on how much works you want to do , and in general I never was a fan of too big weapon specialization on classes (I like my classes to have the ability to use a bit of each, even if they get +10% damage with swords they can still use clubs, but if they get +50% damage with swords its starting to not be worth using anything but swords).

Also it seems odd that the mage should have 3 paths instead of 2, you might want to consider making 2 new mage classes, so you have "Mage", "Summoner" each with 2 sub-classes, in this way it won't seem like the mage is loaded with options, compared to the other classes.

Sincerely
~ Kongdej

Warriors raw damage spec, or the Assassins crit spec.
I still were under the impression you would keep the "Marksman" trait in the Assassin tree, boosting accuracy and piercing damage. This would just give each type Assassin the ability to choose archery, and then go the direction the player wants with his hero, instead of being dead-locked into "If you are an archer, you have to do it like this"

I completely (and respectfully) disagree, while they have access to magic, you are basically saying "Mages should be better with more choices, because I like Mages better" (when I translate it anyhow). Assassins and Fighters are still half-mages with the ability to cast Firedart, no reason to try and lock them into the Mage class just to use they're spells.

If you spend even more time on a mod or whatever, you can make a buff class, which would be good at boosting summoned or trained units.

I always thought governors should have the "General" traits (boosting the army), so I like this, I just hope I can mix-match these, or at least generals have a slight bonus to city governing, and meaby Administrators can pick 1 or 2 army boosting traits.

Not sure about a capstone giving road building, but its not too bad I guess (and I can't figure out what else it should be, except more unrest reduction and more growth)
You could move road building to the Governor trait itself, and move the normal Governor bonuses to the capstone (meaby boost them?). But that is up for you to balance, I like the general concept around Governors.

Note: these are also based around my own ideas and opinions ofc
Edit: Went through a few edits to make the post more easily readable and correct some words.

Sincerely
~ Kongdej

For governors: Anything that a city produces increased by a percentage as the skill improves. Food, production, research, growth, construction time, unrest, militia/defenders (increase hp/armor/damage), increase effect of city specialization, add essence slots in city where stationed, decrease likelihood of monsters attacking, equivalents to outpost upgrades, decrease in shopping costs, increase in xp gained of other units in city, increase in viewing range of that city, or cities in general, or even the equivalent of another Capitol for that city and any cities attached to that city's ZOC.

IMHO, a good administrator should be able to make magic out of a bureaucracy, enabling his armies to perform beyond what's expected simply because they always have what they need.  Instead of roads, make his truly dynamic, like the ability to summon up recruits to march off to war with his oration (spend population to rush unit production), or get a unit where it's needed long before it's expected to be there (teleport a unit across the strategic map).

The one drawback of the administrator is that he performs best sitting in a city, which is the most boring way to use a hero in gameplay.  It does present an interesting challenge (do I keep him adventuring to gain more abilities, or sit him in the city for more short-term gain?) in the early game, but makes him forgetable in the later stages of the game.   Having an ability that he has to activate makes him more memorable 

The more I look at this problem in the files and ponder how to pursue Paths and Sub paths I wonder why the stats were removed from the game.  Incremental increases in stats allows more diversity and places to sink points that give a potentially wide range of effects depending on the ability choices associated with them.

Strength for warriors

Intelligence for mages

Charisma for Governor

Dexterity for Assassins

Constitution for Defenders (However I am proposing removing this sub path as it is somewhat redundant)

Potentially Charisma for a Summoner (For every so many points it would raise your summoning level by one)

Within the game the stats are currently implemented as such within the code;

So the code is all there its just not implemented.

I don't know I am on the fence on this one as I like direct stats as they can be applied more widely than a single perk point.  You get perks but each is independent so nothing grows they are all static except for the rare traits that are level dependent.  Making perks stats dependent would make them more dynamic.  Then make general perks that raise base stats and in game items as loots that raise stats by 1,2, and 4 points.  Maybe wishful thinking but this seems like a long term good thing to bring back.