But they won't (likely) have uncontested use of the 100s of miles of airspace getting to within firing range, maybe an F-22 or F-35 might slip through but no way an F-16. And while Russia might be incompetent enough they might pull it off once, they aren't so incompetent Ukraine would be able to replay that card.
I’m not sure how secure Russian airspace is, past its not half as secure or capable as I expected. It would be great if the Ukrainians could slip in and out undetected but it isn’t crucially important for success.
I’d expect once shot down the bomber would be escorted. That alone is a massive win.