Hello! I am the maintainer of the DO WordPress one-click image and implemented these changes. Our primary goal with these images is to keep them as close to a stock installation as possible so in almost all cases we simply use Ubuntu defaults. As to the changes you mentioned:

1GB RAM droplet requirement - The change in this requirement was due to MySQL's tendency to use the available ram on a 512MB droplet and cause crashes. Since this image must work on all droplets from the smallest up to the largest we cannot simply optimize for 512MB droplets. In order to prevent crashes after a few days or a week we opted to require at a minimum the 1GB droplet size. It is still possible to set up WordPress on a 512MB droplet by using this user-data script which while not the exact script used to create one-click images, is very close (this is a bash script while one-click are created with python fabric scripts). This script can be pasted into the user-data field on the create page. If you create a 512MB WordPress droplet it is recommended to set up a swapfile and/or optimize MySQL and Apache for lower memory use.

I am not entirely sure of the .htaccess change you are referring to

The change to the web root was an upstream change that was included in Ubuntu 14.04 and newer. When our image was switched from Ubuntu 12.04 to Ubuntu 14.04 this change occurred. You will find that installing apache2 on a stock Ubuntu server will result in a default web root of /var/www/html