Firstly, a few points needs to be made about the compression ratio of this engine.
You imply you wanted it to be for "everyone", so people could choose what they wanted to do with the engine. You come across as though you're making this argument in a way that implies EVERYONE wants to turbo this motor. That is doing the exact opposite you want of this car. Making this car able to be turbo'd easily would require lowering the compression ratio, doing this would then mean the people that want to keep the car NA are shafted. If you then still wanted a decent power level (200hp NA) at that lower compression, Toyota/Subaru would have had to put a lot more time/money into developing a high-power low-compression NA engine, raising the cost of the car itself which then takes away the market of the car.
Point 2 about DI - BECAUSE of the Direct injector cooling the cylinder + air/fuel mixture, you can have a higher CR without detonation. A good example of this is the IS-F, which I believe has a 13.5:1 static compression ratio? If 13.5:1 is the "limit" of an NA engine w/ DI before detonation, then this means this engine (4U-GSE/FA20) would be much more suited to a turbo than a port-injected engine running a 12.5:1 CR. It certainly isn't impossible to add a turbo at that compression ratio, it just means you can't run as much boost.
Finally - IF someone plans to change the rods, in most cases I have seen, they also change the pistons - meaning your points about the shape of the piston are likely next to moot.
With every new car that comes out there have been problems with modifications - In Lexus/Toyota's case, it's the ECU, with Nissan's GTR it was the gearbox and warranty. This car will be no different, and it will also be no different in the way tuners and modifiers come up with solutions to these problems. If the Direct Injection really does turn out to be a problem - block off the supply to the DI fuel rail... If the ECU doesn't cope with this well, replace it... If the piston causes problems when changing the rods, then swap the pistons out for flat ones, and swap the headgasket to lower the compression. I think you get my point. People will mod this car no matter what it takes, they wil continue to mod as they have done for a long, long time.
And if it's all too much of a headache for you to be on the cutting-edge of modding, then find a different car!
