2017 Fiat 124 ABARTH
This can be done, with a caveat. You can remove the upper screen/control. Behind the screen is enough room to fit a standard DIN chassis. You can then bypass the weak factory amp.I wish I could gut out the Mazda infotainment system and replace it with an easy-to-use, stable, up-to-date unit, that doesn’t require a combined degree in electronics engineering and computer science to get it done.
(Bypassing the amp is something I've already done. I have a trunk full of amps now, see below, but there are small powerful units that can be discreetly tucked away)
The caveat is there are a few controls that are only accessible via the touch screen. On the upside, these are all 'convenience' settings such as maintenance reminders, DRL settings, etc. How often do you change these? I haven't since I set them once. The other is the steering wheel controls, but I've got some ideas for that as well. This might be my next project as my factory touch-screen has begun to de-laminate and I can buy an entire aftermarket infotainment unit for less that what Fiat wants for the screen.
It really doesn't require any engineering degrees as it bypasses all the factory electronics, where the complexity resides. Remeber swapping out the factory radio for Pioneer/Kenwood/Alpine back in high school? That simply takes patience, not technical skill.