I don’t think there a way other then C++, which you could loop element adding in constructor and CDO would inherent that.
But you always have option to set defaults on actor start up, with array is actually easier as you can always check size of set array. Could fill array with default content in run time (Construction script or BeginPlay) not sure what you trying to dp but for example, let say you add 16 elements to empty array if defaults, on begin play you would check the size of array and fill rest of array with generated default content.
Also you need to do this just once, doing 100 should not be that much of a big hussle in base class or other classes will inherent and in future you can copy paste properties (yes you can right click property and copy paste there settings)