They can be kept indoors, but I wouldn't recommend it, unless you don't like your neighbors (edited to add) and you want lots of interrupted sleep from the crowing. You can do a search of this site (using the search tool near the top of the page) as one of our members asked this very question a year or so ago. She was doing an article for her blog on keeping quail indoors, and wanted some input from members with some experience on this subject. I don't recall how the thread went, but I do remember several other members replying.
Just my experience, over the past month, I had 24 chicks in a brooder that I kept in my den because I didn't want them outside in my garage because of the cold weather. I had to change the brooder every 2 days as the build up was pretty "intense". When I transferred them to other cages as they outgrew the brooder, there was dander all over the place, and I had to vacuum and dust almost every day. Also, some of the roos have recently found their "crow" and are acting "like a non-stop 6 year old that was given a whistle", if you know what I mean.
About the cage plans, there are several links to threads inviting others to post pictures of their cages that you can search for (key word, "show me your quail pens").
I hope this answers your question,
James
