There are managers that have a tactical nous for starters and wouldn't f*** about with things all the time. A good manager would be able to get us playing decent regardless of new signings. I would take just about anyone right now to get rid of him as it can't be worse.
The restrictions around the players we sign are a problem but look at our squad as a whole and we should be able to deliver some sort of consistent performance every game. yes we will win, lose, draw some but hopefully would not be at different ends of the spectrum every time we play
I agree with your second paragraph but come back to the original question - who would replace him that's better? Sure, there are good managers out there but none of them fit within Ashley's restrictive criteria. In fact, I'd go as far as to say that because of this, anyone we get in after Pardew would likely be worse.