I'd like to make a cheat race/faction/leader to understand options!

create a custom race and edit the xml file to add whatever talents that you want

Where are the appropriate XML files stored?

in your documents folder.

you can find all the faction traits and whatnot in the core files

Okay, I've been doing this... but I seem to be unable to get 'Henchmen' or 'Golems' in any faction other than the faction they initially started as... how do I get those benefits to function PROPERLY in, say, a faction with the Mancer speed traits?

That's a little more tricky.  Henchmen are tied to the Altarian racial type, so you'll probably need to create new henchmen unit entries if you want to use them in another faction.  Not sure why golems won't work, though.  You should be able to just copy the ability from the Gilden blood tait

I have not modded this myself, but I have done light mods successfully, so here is my guess:

This folder:

C:\Program Files\Steam\steamapps\common\FE Legendary Heroes\data\English

Find coreracetypes.xml 

Next, copy and paste these lines into the appropriate lines of your custom race's .xml file:

"<GenericUnitType_Other>Unit_IronGolem</GenericUnitType_Other>"

and

"<GenericUnitType_Other>Generic_Henchman</GenericUnitType_Other>"

Coreracetypes will also have juggernauts, if you want to play around with them. 

Okay, as best as I can figure, that doesn't let me actually research the Henchman tech -- which I think is the issue.  How do I enable the research of Henchmen and Iron Golems?

It worked when my faction had the right race type, but when I changed the race type, the ability went away...

If the faction has the generic units available, they should appear in the tech tree, and be available on unlock. 

Have you tested this yourself?

No. You are the intrepid explorer here.  : )

I think it will by looking at the standard CoreRaceTypes.xml. Those generic unit "other" types are the only lines that designate special units types, even there. The UI makes it seem like training golems or henchmen is a "trait" but the .xml doesn't treat it like that. 

But if it doesn't work, I don't think it'll cause huge issues. And the custom faction .xml is easily edited back.

Save your .xml files in another folder if you are worried. You can paste back the originals if there is any problem.

You need the Race of Men in order to research the tech Henchmen.

If you choose a custom race with the race of men, then you should have access to the henchmen tech.

There are ways of giving this tech to you otherwise, for example, just make it a trait that costs 0 points and you can choose all the traits you'd like.

As to the generic_other unit types you can only have 3 (that's it 3). Male Female and Other. So, you will have to measure these abilities seperately. But doing exactly what you are doing you will fail to understand the mechanics of the game as you are changing the mechanics of the game (quite a bit).

Another technique is to build a faction of every blood type with the same EXACT name. This will enable all troops to be trained for you (just a simpler way to do what you are doing).

In doing this I am not specifically figuring out a strategy -- yet.  I am figuring out mechanics and which abilities do or don't have synergy.  THEN, with a normal race, I'll figure out strategy.

I don't think the 'exact same name' thing works -- it creates two files for the leader... it doesn't merge them, as far as I can figure.

I meant to say faction... sorry about that. It was a bug that was reported somewhere. I'd figure you could use it to great effect that way.