I understand what you are saying but first, I’ve already outlined available apps for the desktop which means it’s not restricted to mobile phones and tablets. Please refer to the list of apps that I have linked.
Second, not sure how a user managing his own DNS would be more secure than our DNS. We take every security precaution with our DNS hosting accounts and use CloudFlare for added protection.
The issue isn’t the size of the SD but the speed of the processor and Ethernet controller. These make it very slow and incur a high failure rate. Furthermore, not all devices have an SD so depending on that cannot work.
Regarding the SSL/TLS support, no Arduino could support this and instead depends on other measures for security. We are looking at cloud access instead of port forwarding in which case we will use AES 128 for communication. In the mean time, you may setup a reverse proxy that adds SSL and even BASIC auth if you wish, as the app does support this.