Seven was brought onto the show to get more young men watching (thanks to two big reasons) and to try and boost ratings--much as how Worf was brought into DS9 in S4.
But what if the PTB had left her out and the series had just continued on as it had, would it have made it to seven seasons or would it have been cancelled? Would ENT have been produced had the show been cancelled?
Judging from s3, I think Voyager without Seven would have lasted maybe 5s before they pulled the plug if they didn't use another "Jump the Shark" stunt to boost ratings like kill off a character or a wedding.
Would the character have gotten as much attention if it'd been male instead of female?
William Shatner refuses to allow it.