can I switch that electronic ignition starting with an old-school key?
No. At least, not anywhere near 'easily'.
That ignition switch, from what I can see, has about 13 low-current wires.
At least a few of them are data lines (CAN bus!). It also directly controls the steering wheel lock (ESA lines).
And another snippet:
That's very different from an old-...
Yes it can be done. There are various options depending on the fault. I have got around every fault the ignition module can give someway or another.
If the key turns and but the steering lock doesn't unlock you can buy a emulator for this and wire it to ignition live or have it on a switch.
If the key turns, the ignition turns on and the starter turns over ...