I wasn't even thinking about housing when it came to things to do during the stress test. Breaking the servers is the point of a stress test, not breaking the content (that's for beta testing).

As for your specific ideas, I don't think you'd be able to get everyone to bid on the exact same plot to push the lottery system to any limit it might have for entries. We know it can handle at least 1000 entries thanks to Balmung.

On deleting a character after bidding, I doubt it would change anything about how the system works. If the characters wins, it won't be able to claim the plot so it would rollover to the next lottery period. If it loses, it won't be able to claim a refund. It wouldn't be an effective way to exploit the system on the live servers (but it would be very expensive).