custom class changes

[fooliset]

Greetings,

I am wondering if it is possible to add new abilities to classes that occur passively, like procs or through other passive action. Examples:

Rogue cannot backstab from behind 3 times, on the third time, do a frenzied attack that does 8 regular attacks in a row.

Shadow Knights passively proc lifetap on attacks for 2*level hitpoints.

Warriors gain 10 attack power every 10 seconds they are in combat.

Shaman's gain Spirit Rage proc that increases cast speed by some percentage.

Clerics attacks can proc a group heal.

I have some C++ experience, but I am confused if things like this need to exist in the client or if its possible to utilize other things (spells, etc) to make things like this happen? If its possible could someone point me to the code where a change like this might be possible?

Thanks,

- F