Hello folks!

I stumbled across EB2 a few days ago and it's awesome! It has a great immersion, lots and lots of detail (i.e. reading material) and (most important of all) a realistic combat experience.
I can see why people love it. (warning: Stainless Steel / Third Age / Call of Warhammer heretic here - well, when I play video games, anyway ... )
So, bottom line: good work porting it to M2TW guys!

Now, since this would be harder to do on the other mods (more buildings to check - you'll see why in a minute) IMHO, it just might be doable here - but, then again, I'm not a modder - so what do I know? Modders, let me know how complicated it is.
You see, it's relatively easy to recruit an Army (non-mercenary, I mean) with all it's troops in (more or less) historical proportions when you're playing a wargame - either take DBA/DBM/DBMM as a guide or use something like: each Army gets 1d6 Archers, 2d6 Spearmen, 1d6 Cavalry. Naturally, you can't do that here, so I'll have to mod the Idea bit and throw out:

Historical Unit Ratios.

And by Ratios I don't mean Ratings or Rations - I mean the total amount of troops of that type compared to the total amount of all the troops in all your Armies.
You might also think of it as a 'share' of the army's business (or a 'cut' of the army cake) if you will. (and please pardon the pun - it was totally intended)

So:
1. you determine the 'Current' ratio (or percentage) of a unit type in all of your Current Armies / Garrisons,
2. and divide it by the 'Ideal' ratio (or percentage) of that unit type able to be recruited in your Settlements (Camps) (according to the absolute Maximum number of units that can be recruited stat found in the description of the Settlement's government type - that's what made me pitch this: less buildings to check)
3. you'll get the modifier to that unit type's basic recruitment cost.
Note: just recruitment - not upkeep. And no Mercenaries, either.

So, let's see an example: (to make it a bit clearer)
I'll use my capitol and 3 neighboring provinces in my current Sabae (Va-Va-Voom anyone? I blame it all on randy old goats myself ) campaign for this:

So, if my total 'Current' Army Composition is something like this:
a total of 20 Units with:
6 Royal Infantry (30% of 'Current' Army)
1 Noble Infantry (5% of 'Current' Army)
8 Arabian Spearmen (40% of 'Current' Army)
4 Arabian Archers (20% of 'Current' Army)
0 Arabian Swordsmen (0% of 'Current' Army)
0 Arabian Slingers (0% of 'Current' Army)
1 Horse Archers (5% of 'Current' Army)

And my 'Ideal' Army Composition (according to all my Settlement's Maximum units available description) is something like this:
a total of 40 Units:
5 Royal Infantry (12.5% of 'Ideal' total)
6 Noble Infantry (15% of 'Ideal' total)
8 Arabian Spearmen (20% of 'Ideal' total)
5 Arabian Archers (12.5% of 'Ideal' total)
8 Arabian Swordsmen (20% of 'Ideal' total)
4 Arabian Slingers (10% of 'Ideal' total)
4 Horse Archers (10% of 'Ideal' total)

The next time I go recruitin' units, these would be the prices I'd have to pay:
Royal Infantry will be 2.4 times more expensive (30% / 12.5% = 2.4 times bigger ratio) so ~3500 mina instead of ~1400
Noble Infantry will be 3 times less expensive (5% / 15% = 3 times smaller ratio) so ~200 mina instead of ~700
Arabian Spearmen will be 2 times more expensive (40% / 20% = 2 times bigger ratio) so ~1400 mina instead of ~700
Arabian Archers will be 1.6 times more expensive (20% / 12.5% = 1.6 times bigger ratio) so ~1100 mina instead of ~700
And Horse Archers will be 2 times less expensive (5% / 10% = 2 times smaller ratio) so ~700 mina instead of ~1400

You'll notice that I left Arabian Swordsmen and Slingers for last - since, according to this calculation, they'd have a recruiting cost of 0.
IMHO, that's just as it should be - since recruiting is mostly about offering incentives to people with equipment to come and join your army. And when everybody else has left to fight (and get some cash) the people nobody wants will be eager to get into action (with all the loot entailed) at all costs. OTOH, when you have already gathered most of the available soldiers of a certain type, you'll find you have to give out more incentives in order to gain more troops. Again, just as it should be.

The same principle might be applied to fleets, as well, since (as far as I can tell) size of the Port only determines the number of ships that can be recruited.

Keeping in mind that, again, this is just about recruitment, not upkeep.

Again, this is just my 2 cents.

Cheers!