One of my principles of where to place XP bonuses from buildings is that military
doctrine does not necessarily keep up with military
technology, and that I think it is more interesting if the ability to add XP to a new unit type is not available immediately upon unlocking the new type. For example, this is why
Archery Range does not appear until
Athletics, forcing your first Archers to be lower in XP. Likewise, the transition from Melee to Gunpowder units needs some planning to pull off for maximum XP, because Arquebusier and Garrison appear at separate techs (although Leadership and Matchlock are on the same column, rather than Leadership appearing later). By the Modern Era, general military science is developed enough to where this is harder to justify, but it feels correct for earlier eras.
Another thing that I want to be careful of is over-proliferation of XP on a specific unit type. This results in "curve-breaking" or units starting out with too many promotions. A well-established civilization should be able to train fairly high-quality units but not exceptional quantities of them. The really elite units (taking advantage of West Point, Red Cross, National Redoubt, or Secret Army Base) need to come in smaller quantity.
What this translates to is I want to institute a couple cuts in the XP bonuses from buildings.
Garrison
- No XP bonus to Wheeled Units
- No XP bonus to Tracked Units
Garrison is available from the early Renaissance era. Wheeled and Tracked units start showing up in the late Industrial. I think it would be better if players had to wait until
Logistics and the
Military Base to get XP for these types of units.
Military Base
- No XP bonus to Helicopter units
- No XP bonus to Recon units
Helicopter units have two entire building lines that are granting them experience; the Military Airbase-Aerospace Complex line (+3/5 XP) and the Flight Simulator-Holographic Flight Simulator line (+2/4 XP). That means that you can start Helicopters at +3 XP (Military Airbase is available at Aviation; Helicopters don't appear until Aerodynamics), can increase to +5 by the end of the Modern Era, and jump to +9 by the end of the Transhuman, not counting general XP bonuses from buildings (like Universal Soldiers), wonders (Pentagon), or civics (Standing Army/Volunteer Army). The +2 from Military Base is unnecessary, and it would start Helicopters with 2 promotions from the very beginning; I don't like this, so I think the bonus can be cut.
The reason for cutting the bonus to Recon units is that it's never likely to be used. The last unit in the actual Recon class is the
Adventurer. The
Motorcycle is classified as a Wheeled Unit, and so you would rarely have a situation where you could build a Recon unit that would get an XP bonus from a Base, unless the city was cut off from Oil Products and Vulcanized Rubber. In that case, I think you wouldn't be building scouting units; you'd be after defensive and offensive combat units.