I've worked in many professional radio studios with different radio automation systems in my years in the industry, some costs 10s of 1000s of $$, and hell, before computer automation, I was plugging tape carts into a cart machine to play music.
One thing I can absolutely say, is that I have never and probably never change, is that a audio console/mixer will always be in the audio chain and an automation/playout system will be just that, and always come up on a pot (s) on the console/mixer.
This is common sense. most radio studios have multiple mics, and multiple sources even today. You have to put someone on the air from a phone hybrid, you need to run that through a console....a satellite feed, remote line via a IP codec, etc. all come up on a separate pot. No professional studio has just one mic and the automation system. multiple sources WITH the automation system goes through an audio console.
As I collect vintage radio studio gear, and have both a control room and production studio for my internet stream, I can play off vinyl, tape carts, and even reel to reel tapes to air to the stream. Like any pro studio, the automation system may run the station, but it loops through a console. This way, you can kill the automation system at any time and go live with CD/cart/reel tape or work with it and go live assist.
My on air console runs 24/7 is analog and is 45 years old and sounds great for it's age. It's cheaper then the new digital consoles that can run upwards of 15-30K being installed in studios these days which keeps audio digital in the ip audio domain, but it does the job well. I'm all about vintage.
I usually don't believe in software audio processing, as it can slow a computer if you are using real time. I use a basic compressor/limiter in the audio chain. I turn off anything radio DJ has built in for EQ/compression. There are too many "commerical wannabe's" on the net streaming and think sounding like a commerical station's overprocessed severely compressed (in some cases "brick walled") is a good thing. It's just terrible most of time. In a digital world, destroying dynamic range is terrible. Google if if you don't know what that is. You should.
Bottom line, a mic switch is useless for an radio automation system. It maybe useful if you are doing mobile DJ type stuff off an computer, but not in a radio studio. Buy a mixer, and use other sources too instead of just playing off the computer.