All combat equipment in the modification is thought to have some implications on the performance of the soldier. As familiar, a cuirass would improve the soldier's armour. What we've done is to add an additional function (or lack thereof) for a lot of equipment though. The type of armour worn by a unit does not exclusively change its ability to mitigate damage, but in some cases reduces manouverability and therefore the defensive capabilities of the unit. As a rule, the heavier the armour, the lower the flexibility. The construction plays a relevant role in this as well. This meaning, there will be a trade-off which you have to form an opinion about. Similarly, armour is going to play a part in the recruitment and maintenance cost of a unit.
Shields are no exception to this. Smaller, more manouverable shields will often have superior defense but less coverage (protection against projectiles). Every shield, with a few exceptions, will add an offensive bonus to the wielder. How large this bonus is depends on the shape, size and weight - smaller shields will typically have the upper hand in this. A Caetra, for example, gives a unit +2 attack and +5 defence, but provides less protection against missiles. A Scutum, by comparison, gives +6 defence but only +1 attack. As larger shields are tougher to manouver, the intention is to add a flanking penalty of sorts for units using those. Units with smaller shields will retain greater agility and therefore be more flexible on the battlefield, capable of more effectively dealing with threats on the sides - unless they rout first!
When it comes to the weapon, each is thought out to have a set of techniques which with it could be used. Spears would have been used primarily for thrusting, while swords and maces on the other hand could be used to cut, thurst or bash someone with. The amount of techniques a weapon allows plays a significant part in determining its attack value. Certain techniques will be more valuable than others and therefore provide more attack points. Precision is another measurement of its effectiveness in combat. As a rule here, shorter weapons will have greater precision, as any movement with the weapon will be more in line with your body's (arm) movement. It's seen as how effective the weapon is at overcoming enemy evasive measures - a shield or just movement, essentially. Longer weapons such as spears will be less precise, partly because it's also harder to strike in the right place at greater distances. Pikes have the least precision of all weapons, but will be superior in other regards. Two final measurements of effectiveness would be initiative and rate of strikes. Initiative is just what the name implies. Longer weapons will provide greater initiative, but it's also seen as a psychological aspect of combat that can be modified based on what we call "troop mentality". Rate of strikes is, to make things short, how quick aggressive initiatives can be mounted. The final attack score, equivalent of the sum of these four factors, will be modified depending on various other variables as well, mirroring the greater initiative and comfort with a weapon a more experienced soldier would have, or the lack of initiative and understanding of the weapon's fields of usages an inexperienced soldier might have.
This is where we're at currently. Up next are morale, fatigue, unit sizes, cost and maintenance and various modifying elements to combat prowess. We have an idea of how we want to design/balance these already, but suggestions and requests are more than welcome. The more opinions and experience we can gather, the better the end result will be.
Sincerely, the AE team