You can create your own directory and put as many start parts you require without replacing the default. Here is the config option:
start_model_dir C:\enter full path name here
I found it very useful to actually create different geometry inside different start parts with the drawings dimensioned etc.. You can also have family tables inside your start parts, to have drawings you will need one for each instance.
To change start part for a part or a assembly file.First u group all the features by local so that the group file will be saved as *.gph then u start ur new file with ur start part then u call the group it will ask the references u just give the ref then all the features will be copied to the new one.