Uses for change-type action?

[Emmanuel Fritsch]

 # Well, thinking abstractly, what about units that have essentially the same
 # composition, but react or perform differently?  E.g., an infantry unit
 # that can change to "dug-in infantry" type, and back again?  The movement
 # and combat capabilities would be different for each type.  I could also
 # imagine "infantry mounted in halftracks" <--> "infantry with accompanying
 # halftracks", "fighters in an interceptor role" <--> "fighters in an escort
 # role", etc.

All this could be lead though garrisonning, no ? 

In fact, I do not understand the specific power of 
change-type action compared to build/garrisoning. 

Could you explain ? 

a+
  manu