There were some ADs on these switches over the years. Probably, a lot of maint people don’t do an AD check and somebody finds out the hard way.
albeit not in a position likely to be pushed inadvertently
I would be a lot less concerned if it was thus located, too, but on the TB20 it could be easily kicked.
On some aircraft a key can be removed and the magnetos remain active when keys and switch get worn. There have been several REX to this effect in recent months.
Peter wrote:
It’s been pointed out that this dual-switch thing makes it difficult to check that the ignition is dead. Fuellers and hangar crew like to see a key removed. And I agree.
I can see the reasoning, but our aeroplane has switches for mags and a push button starter (unguarded, albeit not in a position likely to be pushed inadvertently) and I have never ever had an issue with anyone on the ground feeling uncomfortable by the lack of a physical key.
Peter wrote:
Fuellers and hangar crew like to see a key removed.
Whether the key is in or removed doesn’t prove or change anything. I would also trust two separate mag toggle switches like the example below more than the innards of the rotary switch.
Peter wrote:
It’s been pointed out that this dual-switch thing makes it difficult to check that the ignition is dead. Fuellers and hangar crew like to see a key removed. And I agree.
Have a set of gym keys on a linyard for that purpose? :)
It’s been pointed out that this dual-switch thing makes it difficult to check that the ignition is dead. Fuellers and hangar crew like to see a key removed. And I agree.
Bolkow Junior has mags key but not start. A separate guarded push-button operates the starter.
At first I often nearly broke the key twisting it trying to activate the starter.
Can you not buy an aircraft mags and starter switch? They’re available.
I would definitely replace your keyswitch…
The timing to turn the key ccw on short final to shut down the engine and lower the gear looks tricky to me;)
IO540-C4D5D.
I did a google on Apollo Lunar Module engine start switch, and got some ideas on how to make it hard to press it by accident, and also how to label it 
The engine won’t be startable unless you have main power on, but the only interlock (to prevent starter activation when airborne) I can think of would be bus voltage under 26V (main alternator voltage regulator is set for 28.0V and the backup one is set fo 26.5V) but you can’t do that without “electronics” even though it would be only a few components.
could trash the engine
Too lazy to check what engine your TB has, but methinks that “only” the starter and flywheel would be in danger. And yes, my ship sports a starter button with side guards 
