Modding questions

[PrinzMegaherz]

These things might have been asked before. I tried my best with the search engine, but did not find what I was looking for. I really would appreciate your help :-)

1) Is it possible to add spell effects to new weapons? I would like to create a bow that fires ice arrows / does ice damage and freezes the enemy

2) Is it possible to mod "after death change" like Lamia or Shapeshifter to new units?

3) Is it possible to add the normal change command to a commander (like Dragon)