[Brightcolours]

The A99 is a great camera but it has hardly a significant USP over Canikon.

Not entirely sure what makes the A99 a great camera, when you really look at it. It does not have an OVF, it does live view all the time so you can run into heat issues (especially with its closed sensor compartment), and its AF tracking ability can not hold a candle to what the Nikon and Canon FF models offer (including the much cheaper 6D and D610).

 

It might look nice spec list wise for some, but in practise... 

The A7® has some.

 

Honestly I do not think that the system argument is that important on a broader basis. Most amateur photographers could be happy with the initial set of lenses.

Professionals are a different story.

Amateur photographers who are happy with just an f4 standard zoom, a 55mm f1.8 and especially a 35mm f2.8, should not even be looking at FF, as the main advantage of FF is the possibility of shallower DOF. And for that, one needs to look at adpated lenses (A-mount, EOS-mount, M-mount).