Mesh Technology - Lets you enjoy an enclosed porch when the bugs are out.
Hardware/Software Separation - You'll get along with your spouse better if you have separate bathrooms (particularly toilets) and separate closets.
Social Media Integration - Parties revolve around the kitchen, so ideally have nice flow between the kitchen and (as applicable) the living room, porch, and dining room. In my case, I really don't want guest helping with the cooking or dishes, so give me a design that fences them off with a bar-top counter, but keep it open enough that I can peripherally participate in whatever's happening in those other rooms.
Dedicated I/O Path - Your pantry should be between your kitchen and garage/carport, so unloading is fast and easy. Also include a small desk and file cabinet for processing mail and keeping keys/wallets/purses out of site.
Security-Hardened Design - Minimize number of entrances; ensure perimeter and walks can be fully lit; install alarm system; include tornado shelter (if applicable).
Non-Paged Plan - This is VERY expensive, but you'll appreciate the absence of stairs if you spend your retirement years here.
DRY Principles - Make sure site has adequate drainage, that gutters are clog-free or otherwise easy to maintain, that bathrooms can be well-ventilated, that your roof isn't too complicated, and that you don't have a pool. Moisture is the enemy!