There are several ways to modify the game, and ACE or other mods.

Essentially through official Configuration (Userconfig, global variables, config variables etc) and API (see also Resources), but obviously the game is extremely modable, as evident by the many great mods and addons that are available to the ArmA series.

For example, you can use existing addons (for example see Compatible Mods) or even write a simple override config and change/override/replace or do whatever you like :)
You can modify, remodify, etc it to pretty large extents; go wild and configure it to your heart's longings!

For great examples of simple yet effective config overrides, take a look at kju's "PROPER" mods, or perhaps other replacement configs. Otherwise the BIKI, BIF, OFPEC and resources at Dev-Heaven.net could provide you with info and aid.

Another method is overriding functions/scripts.

If for instance your values are found to be superior to our own, perhaps you can submit it back as patch, and we could include it, while crediting you as author. See Contribute for more info.