Personal opinions I spose. I play on Pro and find it about an enjoyable game of football I've played. No football game is perfect, there are just too many variables - millions. Its impossible for them to cover everything.
I'm saying there are more pressing problems now than on the pitch issues for me.
I guess anyone playing on the hardest difficulty will find room to complain, but it must be exceptionally hard to grade difficulty in football games and its always going to appear 'cheaty' at the highest level to give you a challenge.
If they scrap this engine and start again as you suggest, they may never get here again (which is why I say that fundamentally, PES will never change, Gran Turismo will never change etc - its the games DNA).
Tweak it sure, but how much more tweaking can this engine take? The big problem with FIFA is that as a 'whole' its flawed. The front-end engine is creaking. Its hard to navigate, cannot edit much and anything you do edit either gets corrupted or overwritten. Its just not user intuitive any more.
If THAT was improved, then maybe we could get proper sliders and make the game how WE want. Perhaps share the sliders - i.e. if we played each other, then average out our joint sliders so its a fair game.
I dunno... still... 2 weeks till PES

Despite the rush of sales of FIFA10, if any of this bug stuff gets wide spread (and it SHOULD), then PES could be nicely placed to pick up some sales from trade-ins.