Modding Bonuses units get from experience

Ok, I don't know if this is an easy question to answer, but here it goes. In
M2TW after a unit gains experience from killing in battle, it's stats are changed. I noticed as a unit gains experience it only gains defensive skill, no attack changes, and missle troops never gain missle skill for all the people they kill with their ranged weapon. So the question I pose is this, can this be modded?

Can a melee unit gain attack skill when it gains experience, and can a missle unit achieve a greater ranged skill from gaining experience?

Any help would be greatly appreciated.

No it cannot be modded.

well thats a bummer, I guess it is one on those things that they call hardcoded, right?

Yes it is. For such things you'd need an SDK for to make them properly (i.e. the ability to compile some parts of the game code) because it would probably be too slow to make them dynamic - not to mention a lot of work.