It'd be cool if the house actually served a purpose beyond spending hard earned credits just to decorate it. Like maybe the people that visited would battle you. Be able to use the radio (that would be nice!), sleep in the bed, use the computer (what the hell is up with that?!). All in all, it definitely is a waste of space and time. Not worth any effort.
I have to agree with some of the things you said. They could've made the radio play music. Maybe it could even be similar to the one in Gold and Silver.
Though not using the computer is something that I don't mind. What could you do on the computer anyways? Mini-games would be cool, but the Battle Frontier has those things already.
The people battling you would be nice because not only can you gain levels for the Battle Frontier, but it will help you train for a variety of things such as contests, for the fun of it, Elite Four, and many more. It could also help you EV train, but that would be hard as I could picture them having a various amount of different pokemon that can help you EV in many different things that you wouldn't want.
Maybe instead of buying the things for your Villa, they could've used coins. It would've been helpful, and to gain coins you can go underground and find them commonly. I highly doubt that would happen, but it is an idea that could be useful.