AVRs are superior to all other processors in their class because... I can make them do whatever I want in minutes (many times less than 15). There aren't gotchas. Violating their datasheets is the best way to spend a Sunday afternoon. the hardware can be reconfigured soooo many ways and be abused so wonderfully. They are extremely tough when it comes to being blasted, shocked, having insane currents sent through them, etc. The ASM instruction set is so wonderful, so carefully crafted, such wonderful commands and so powerful, operating at the system clock.
If it weren't for the venerable ESP8266, I would likely have spent all of my free time working with AVRs and only AVRs.
I say this mostly to challenge you to go implement it on a processor better suited to this problem. If I'm right, I'm right... but if I'm wrong and I have to eat my words, I get a free lunch from you. I will mandate that any further discussion on the topic of coprocessors must be predicated by you demonstrating a fully functional one using a better processor.
Regarding the controlling from a phone... I don't actually own a smart phone, but, I want to develop an HTML 5 app with multitouch to make a multi-plaform, web-only interface for flying it. I have done a lot with WebGL and WebSockets. Both of which are phenomenal, and I want to bring to the ESP8266.