I couldn't simplify to just classes or just attributes because the classes don't mean anything without attributes, and only units with classes can have attributes!
Final Proposal #360:
Units represent people. Each unit can have one class and any number of attributes. Attributes and classes are defined by rules, and should be capitalized.
Classes. A unit can be placed without a class, or assigned to a class at the time of placement. Each class has unique abilities. Assigning a unit to a class costs 1 IP and can be done at any point in the player's turn by posting in bold Assign Unit at ## to X class. Units can change class, but they lose all their attributes. Units of different classes are identical when all attributes are at level 0.
This rule defines the classes Farmer and Soldier. Their special abilities could be reflected in attributes such as skill, productivity, tools, etc. Farmers are represented on the map by a block "F" in the player's color. Soldiers are represented on the map by a block "S" in the player's color.
Attributes. Attributes give units new abilities or increase existing abilities. Some attributes affect all units the same way, others give abilities specialized to the unit's class. A unit needs to belong to a class in order to be assigned attributes. All attributes start at level 0. Abilities at each level depend on the attribute. To raise an attribute up a level costs N$25 and 1 IP and can be ordered at any point in the player's turn by posting in bold Unit at ##: Raise X [attribute] to level Y [the next level]. Pay N$25. Raised attributes take effect immediately, so they can be raised and used in the same turn, including the turn they are placed. However, any given attribute can only be raised one level per turn per unit.
This rule defines the attribute Speed (abbreviation Sp.). Units at level 0 Speed move one space a turn. All units at level 1 Speed can move 2 spaces per turn, at level 2, 3 spaces per turn, and so forth. This attribute is currently the same for all classes.
This rule also defines the attribute Skill (abbreviation Sk.). For Skill, the abilities associated with each level depend on the class of the unit. Other players' units cannot move into proximity with Soldiers at level 1 skill. Units that are already adjacent at the time of the attribute raise are not affected until they wish to move to a new square. Farmers at Skill level 1 get double proximity points.
Attributes are represented on the map under the unit symbol by small print abbreviations followed by the relevant level. For example, Sp 1, Sk 2.