I definitely agree with the sentiment and sure, if you want to try to squeeze the last 5% of performance out of a front engine car, you can definitely do that. However, you do run into diminishing returns. The amount of work and effort to get the last percentage is exponentially higher than it may be worth. I would argue the 13 BOSS 302 Laguna Seca is a good example of the pinnacle of Ford's effort for a live axle performance car. That car outran M3s, then they developed the S550 PP1, which subsequently outran the BOSS 302. Another example in the Porsche/Ford example is the base 911, with it's 379 horsepower, runs the quarter mile in the same time (not trap speed obviously) as the GT500 (real world not manufac. claimed).Engineering is frequently forced to work within constraints that aren't of engineering's own choosing. IOW, do the best you can with what you're given, as long as you stay inside the big box.
Perhaps the poster-boy example of that within the automotive world is one of the cars you just mentioned. I'm talking about the 911 Porsche and its rear engine. If it hadn't been for continuing engineering development over the past 55 years, it would have long ago been consigned to the dustbins of automotive history under 'things that might have had promise but didn't work out'.
Closer to home and as good as they are, both the Coyote and the Voodoo have also had to develop under constraints that you wouldn't choose if your primary focus was on power and performance.
So to you point, yes, is it possible to throw money and engineering at the problem? Absolutely! However, physics is absolute and in this case, it has been proven over the years that weight is the enemy of performance. If the current GT500 isn't a smoking gun, I don't know what is.
Overall, my point was simply to say that a bigger 6.8L engine doesn't give people the solution they think it does. Sure, you can brag about a large displacement number, however, you run into the Dodge Hellcat scenario where you're still losing to cars that have more sound engineering principles for what the end goal is.