About units:
It will be hard to tune units properly because of several things:
1)A straight power/time ratio isn't really correct since the combat system is not linear. A str 6 unit will always beat 2 strength 3 units. It's probably going to take 3 or 4 str 3 units to get rid of one str 6. So better compute str*str/time.
Furthermore, defense bonuses and promotion bonuses tend to be % bonuses, making the advantage of a bigger strength even better.
2)Manufacturing power grows with time as population grows. You can lower that effect a bit if you let something like a Noldo specialist that's available until end of First Age or when an event like 'The Noldor cross the Sea never to be seen again', thus removing a strong specialist, but you 'll have to see that manufacturing power increases as pop and number of cities grow (not counting stuff like forges), so time to build will be a function of time: A knight who took 11 turns to build 100 turns ago may take only 8 turns now.
3)Existing units will have promotions and be very powerful. It's quite understandable that units like Elladan and Elrohir who spent ages chasing orcs should be very strong, but there should really be few of them.
So here's a suggestion for stronger units:
Use Great People. They come more often early in the game because they require less points early on. It's also not very easy to control. If you create for instance a building that adds 1 Elf Great People point and a later building that adds 3 Warrior Great People points, you'll be much more likely to get a great elf hero in the first and secodn age, and more to get a mortal in the third. It can also be a good way of getting Balrogs and such: 1 Balrog GPP per a specific wonder, 2 Dragon CPP per another one, and 3 or 4 other kinds of GPP per specialist/other buildings/wonders.
The GPP are also limited civilization-wise: So if you want to focus on getting Balrogs, you'd have to make sure you don't get any ohter great people anywhere else of another kind as they'd lower the chances of a Balrog appearing (by raising the cost for each new GP to appear).
