I think this could work, I am not sure it is better than the RAW system though.
But here is a simple solution to the Full Attack problem.
At the beginning part of a round if a character can make a 5 ft step and attack, she does so (at their full bonus). If the second part of the round comes around and they can still attack, they choose THEN whether to continue their attack as a FULL attack action, (thus getting the iterative attacks) or not.
There may be occasions where an opponent will see the futility in sticking around to fit after the first part of a round and decide to bolt, thus thwarting the fighter's chance for iterative attacks but:
1. The fighter is not helpless after they leave, she could move, turn on another nearby opponent, or perform some other ME action;
2. If someone attacks in the first part of the round and then decides to move away to avoid the iterative attacks, he is vulnerable to an AOO. Which depending on the AC of the opponent might be worse. So in fact FULL attacks seem as likely as before to me.
There would be the occasion where someone moves to attack you and then on your system you coul dmove away thus preventing them from attacking you (assuming they do nothing but move, otherwise you would get an AOO). But this strikes me as not to serious, after all, if they do move and act you get an AOO which is pretty much as good as a regular attack, and then you get another standard action. In addition, if you win initiative, you can always opt to delay your action to see what other people do first, then move in response to them.
I think the Full Round Casting Time limitation for Metamagic makes it less likely. But to be honest. My experience has been that Metamagic is abused anyway, so I don't think it is too bad to nerf that.
My main concern would echo the problems above, that you are adding a level of complication without obvious benefits to game play. Are there occasions when you think game play suffers when a person moves and attacks in the same round?
S