Please continue to consider offering a web interface that can at least still function without outside connections. I like the new GUI much better than the old, but one of the reasons for choosing OS was because it could function completely independent of other outside network connections. Continuing to be able to host the needed files off the SD card would at least make a good backup method.
That’s why the app is provided, which won’t require Internet access. Any reason not to use the app? The app has the same UI as the web UI, but provides more functionality like scanning OpenSprinkler device.
Also, consider, treating OS as a local device, allowing individuals to decide when/if they want to upgrade.
The firmware is the part that you, as a user, can decide whether you want to upgrade or not.
Frankly I believe most users would prefer an automatic update as opposed to scrutinize every update. Most updates have to do with improving the user interface, fixing bugs. Websites update all the time without the users being aware of them, for applying critical security patches etc. That being said, it’s certainly possible to make UI upgrade also an option that the user can choose. But I honestly think it complicates the decision making, and most users probably don’t want to have this extra choice to make. If you look at commercial products, like Nest, many of them don’t give you any such option at all.
For a technical person like you, you can also find ways around it, such as by replicating the scripts on your local server or internal SD card, which are both supported.