Include information about the possibility to sysupgrade into failsafe page

I'm not sure it should downgrade the wifi.
As for the gigabit fibre (the NAT/routing acceleration issue I guess) while there is still no support for the hardware NAT engine (which is why the stock firmware can do gigabit WAN), there is "software flow offloading" which still increases significantly NAT speed (from 300 to 600 Mbit/s on the v5, and on devices with a slightly more powerful CPU it can do gigabit), as long as you do not use SQM or other traffic shaping. So that's at least "less bad" than before I guess.

This feature is not in the current stable release but will be in the next one that is going to happen in months. It is available on snapshot builds that don't have Luci web interface by default so if you do what the guy did in that thread do prepare SSH programs to connect and install Luci in your device after install.

There are also custom builds of OpenWrt with hardware NAT engine support, they are fast as the stock firmware (obviously), but I can't find the source code for them (only older version of his patches), so you need to trust the honesty of the guy making them.

This is a thread about what I just told you.