Hi Razvan
Your observations are essentially correct. Some specific comments on your points:
1. The WAN interface can certainly be configured as a DHCP client in the SECN web interface.
If you look at the Advanced/WAN page you will see the config for that.
However if you want to configure the LAN side bridge as a DHCP client, that is not something that is currently provided in the SECN web.
This configuration is possible in OpenWrt, so could be set up that way for your particular application.
2. The current web interface does limit the range of special characters in passwords for simplicity.
This is not a limitation of the underlying OpenWrt system and will be addressed in a future SECN interface upgrade.
3, 4. The SECN web interface does not currently support IPv6 configuration.
This is not a limitation of the underlying OpenWrt system which has IPv6 support.
It may be worthwhile posting a query on the OpenWrt forum to clarify whether the IPv6 support is a complete implementation of the standard as you have outlined.
5. Physical network interfaces can have multiple IP addresses in OpenWrt and this is used in SECN firmware e.g. for the Fallback IP address on the LAN side bridge, and for the wifi interfaces. But there is no facility in the current SECN web interface to configure additional logical interfaces with their own IP addresses.
As you will appreciate, the development of a user interface for something like SECN is a compromise between creating a usable interface and implementing all the functionality of the underlying subsystems such as OpenWrt, Asterisk and batman. There is an almost infinite set of combinations of how these subsystems can be combined and configured.
It is not really feasible to build a user interface to deal with all possible combinations of such a system, while still remaining simple enough for users to deal with it effectively.
Rather than build a more complex user interface, a better approach may be to tailor an interface design specifically for your application, and make it more of an 'appliance' than a 'toolkit'.
For example if you have a few standard configurations that you will use in field deployments, then it may be more useful to put together an interface that simply allows a user to select from a short list of pre-defined configurations, with just the pertinent parameters such as IP addresses being displayed.
The SECN firmware can provide a useful base for this sort of development as it has the basic components of the system pre-assembled and working, and a build environment that allows you to make custom firmware fairly easily.
Other alternatives that you might like to consider include the LuCI interface provided by the OpenWrt project, and the LibreMesh project which is addressing large scale mesh networks.
Regards
Terry