can this be done and is it legal?

one family owns the duplex and one side has a swim 5 and the other wants to add a multi sat. if i change the swim splitter to a 1 x 8 multi switch and add the other 4 standard def. to the other side is this legal? it takes out a dish. and the programing for the 4 new standards is on the cards so it should be fine to do and its legal?