What is the Dropship Loadout
The dropship loadout is a feature that was cut from Tiberian Sun late in its development and presists in a somewhat buggy form in RA2 and YR. In TS, the feature was to present the player with a screen where he could purchase units that would be delivered to him as a scripted reinforcement during the mission that followed. The feature could be made to work almost perfectly for single player missions with the exception that the mouse cursor didn't show up, making it difficult to select units. The screen also didn't make it clear that to progress from it, the player needed to press the space key. In RA2, the screen still lacks a visible mouse cursor, but also uses the wrong chracter set for describing the units before purchase. The box draw around icons when they are highlighted is also the wrong size, due to changes in the icon size used by RA2. Apart from these issues, the only other problem is the art work for the screen whch does not fit RA2.
Using The Loadout Screen
To access the loadout screen prior to a mission, the map file must contain the line StartingDropships= in the "Basic" section. The value for the flag must be either 1, 2 or 3 and specifies how many dropships the player will be able to specify the contents of. To actually recieve the reinforcements, there must be a reinforcement trigger that creates a team with only a Dropship unit in the taskforce. The logic should fill the transport with the units ordered.
The player can be limited in several ways as to what they can buy. First of all, they are limited to being able to select units that have the player country set in the units Owner= entry. In RA2, the loadout ignores RequiredHouses= ForbiddenHouses= and RequiresStolenXTech=. There are controls available that can adjust what the player can and cannot purchase as a reinforcement however, as well as how many of each unit. Both of these controls are specified in a maps "Basic" section as well. AllowableUnits= specifies what units are available to purchase using a comma seperated list and is based on the unit section names from rules.ini. AllowableUnitMaximums= is another comma seperated list that has the same number of entries as the Allowable units and sets the number of each unit that is allowed to be purchased (-1 gives unlimited). The TechLevel of the player house/country is also believe to limit what can be purchased but this has not been confirmed. The amount of credit available to buy units is the amount set to be available for the player house, if no credit is available it seems to give an IE when you exit the screen (in RA2 at least).