You should post this topic in Suggestions&Requests. I believe it's slightly more suited there as Gallery, is specifically for completed Blockland Creations.
Also, it's not really possible for us to say whether that idea would look good. It's a really vague description.
A stone and wood house could look like anything, and a Modern Extension could be built in any shape, size or direction.
We don't even know the landscape you're planning on building it in.
Perhaps you could find a real life picture to show the sort of structure you are thinking of.
Your idea could look really well, if done well, or it could look terrible if done poorly. Unfortuantely, we can't quite tell what you're wanting, so, there's not really much to say or any advice to give you.
But, so long as you like the outcome, consider it a great success. Have a go at it and have fun.
