I would suggest making these one model and rigging it, then use findchild on all the bones and just rotate/turn/position the children. This way it keeps everything in the right place and it also means that you can rotate/turn/move the whole thing without worrying about the other bits.
If however, you specifically want to make it out of seperate entities then I would still suggest rigging the main body and doing findchilds so you know where to position and rotate the entities you want to attach.
If however, you specifically want to make it out of seperate entities then I would still suggest rigging the main body and doing findchilds so you know where to position and rotate the entities you want to attach.