Canon could have easily churned out a mirrorless with a 5d mark ii-like sensor in it with a similar body style to the EOS-M, and kept it priced competitively.
Pricing a camera with a FF sensor competitively is pretty hard. Just look at the fixed lens Sony RX1 as a guide. Want a cheaper FF camera? You've already got the D600 and 6D.
Canon is in the business of money making. I'm sure their marketing staff must have done their homework and concluded APS-C is the way of the future. The sensors are cheaper to produce and the accompanying lenses are also smaller. Until manufacturers find a cheaper means to produce FF sensors, they'll always be reserved for a niche market.
I understand that full-frame isn't cheap. I also realize aps-c is at a really good place price/performance-wise. I just think that Canon could have easily leap-frogged the competition with a cheap-body full frame mirrorless (to help keep costs lower.
When Microsoft's Xbox came out back in 2006 (I think), it was as powerful as some $2000 gaming computers, and they sold it for $400. They knew they were going to sell a lot of them, and the games that went along with it, so they kept the price low enough for it to take off. A full-frame mirrorless, priced aggressively, and banking on lens sales to maintain larger profits, could do exceptionally well for Canon. Seeing as they're probably the only company on this planet that could pull something like that off, it's disappointing to have them play it safe in the market with a smaller sensor, and remove a reason for them to make Full-frame mirrorless lenses.
I guess I'm in the minority, but I just think full-frame should be more readily available to the masses (I know somebody's going to say film is cheap). If somebody told me each aps-c sensor costs 50 bucks to make, but a full-frame sensor costs like $1000, then I'm completely wrong and I take everything back