My idea was to cut out all of the extra components and give people direct control from their phones via Bluetooth.
I'm going to play along here.... how are you going to do this without extra components? To my knowledge, there is no bluetooth switch machine. There's probably no bluetooth anything, because DCC functions on the loconet bus and its standardized, and if it involves 3 rail, its all proprietary whatever it is. Also, surely you can't expect layouts to be retrofit by ripping out dozens of switch machines to put in new ones? You're going to need an interface that has a way to talk to existing hardware. Thats going to require an "extra" component of some kind. And it'll need to talk to a lot of different things in order to work.
Just look at DCC. Every time there's a new functionality that comes out, you need another box or module to make it work. Lets just say at a minimum, you'd need a loconet adapter for bluetooth.
I'm not raining on your parade, just something to consider while working your way through this.