The challenge is that if you want to add intelligence on top but still keep the way of simpler controls by wires - it makes the whole system very complicated. This is the same challenge they have in cars. For example to make drive-by-wire system, but still have ability to control the wheels mechanically. This creates all those complex coupling/decoupling mechanisms and associated problems.
So in case of amateur home installation if you do it wrong most likely you will get more problems, than benefits. And architecture selection here is most critical thing.
So that’s why I’m a supporter of completely smart home approach - e.g. you control your home only by controller and do not override it or backup by wires. So yes - if your controller goes down, the light will not work.
In this case you should concentrate on increasing the reliability and availability of controller. I recommend a centralized system and not a mesh. Wireless actuators and sensors are not a problem - they fail independently, so it will mean that in case of unreliable link you will loose just one lamp - which is anyway redundant. But in case of central controller is much easier to manage failure modes and recoveries.
As for backup + restore process vs. redundant hardware - the first will not work in the above approach - the controller could fail when nobody skilled is at home (and most often too), so nobody will be able to switch on the light or power up backup controller. Thus you need redundancy with automatic changeover.
Which is not a complex thing at all, regardless of what others saying: you will just need a clone of your main controller, which can be as simple as Rpi+cloned USB Z-wave stick. And then you buy a couple of cheap Wi-Fi or Z-wave relays - I use Shellys for example. You power your main and cloned controller via these relays and setup them as a simple watchdog relay - one normally off and another normally on - e.g. main controller, when operating, will periodically send on command to one relay and off to another one to reset them. This will keep them in these states as long as main controller is live.
When main controller fails for any reasons it will stop sending the reset commands. The relays will switch and the main controller will be powered down and at the same time backup controller will be powered up. This process will take just few mins and your smart home functionality will be recovered. Yes, you will loose last states and persistence, but this won’t be a big issue - your house will just restart. And your backup controller doesn’t need to be so sophisticated as main one. It can be less powerful and perform just basic functions of the main one - e.g no sophisticated scenario activity, google calendars or whatever. So you can save HW cost.
Simple, isn’t it? If it doesn’t sound like this, just ask - maybe I didn’t explain it clear enough. IMHO this is much less effort, than investing into wired installation and solving the conflicts of local/remote control. I have a flow in Node-red which manages this process, which I can share.