Changing Rank

Is there a way to change the rank of a unit with triggers or jass?
I thought about using chaos ability but it has few problems.
1. Every special effect is destroyed
2. If you have a buff that make your armor or damage stronger
The altered armordamage will be implemented to the unit.

nope, u'll have to readd each special effect (and destroy the other one), remove all buffs and readd them.