Definatly need to fix the QB accuracy bug/issue. It seems like quarterbacks with low accuracy throw very little interceptions and there TD:INT ratio is very good. If this is not a bug, I at least think that the quarterback accuracy should be more crucial to a quarterback. This is not for all quarterbacks, but still effects some of them. Thanks!

Not having a go at you but there are a million threads on this already, and yes it does need fixing desperately.
To (try) answer your query, the reason that 'bad' QBs don't get intercepted as much is most likely down to them not putting the ball where it should be, ie; near a WR etc.. Very rarely will you see a D player make an open-field INT, usually next to the receiver.

There will be significant changes to this in the next version. Currently the code is in alpha and will be rolled into MFN-1 hopefully soon.

Just wondering, when a new code is implemented, how long of a notice do we receive beforehand? Do we find out about such a change 1 season before it is implemented, etc?

It will be announced, and then rolled into every league on its next 'End of Season' phase (so it will never occur mid-season, or even mid-free agency for that matter).