If you want to stay in G ionian, you shouldnt switch from one to another.,
It doesnt mean you cant play all the modes of G togehter in one peice..
its just that they key will change all the time..
playing all the modes will eventually give you the chromatic scale, which is an artificial 12 notes scale that includes all the 1/2 tones..
this scale is used widley in blues and jazz..