if moving the default folder is something that will work for you, then the best will be you do it at virtualbox for the moment, and every new machine will go there
if your requirement is to be able to select per virtual machine where to put the vm, this is done already in vmware from what i understand, and are a couple of tickets/issues open on github for this
i will test over the weekend the command you have shared,, i wasnt aware of that one and seems it may do the trick
i will report back after i test
thanks
alvaro