 :Actually, buildings in historic districts don't deserve their own articles unless they're notable for other reasons.  The district itself is notable, and of course those buildings can be notable, but they aren't necessarily.  A much better idea would be your second suggestion, because having some good details on the various buildings in the district would be quite useful and far better than having a tiny district article such as this one.  As far as the thematic groups (now called Multiple Property Submissions if I remember rightly), ask Doncram, who has done work on these.  After researching the issue, he came to the conclusion that they're not necessarily notable per sé, but having an article on the group and redirecting the various property articles to it would surely not be problematic.    