While accepting the need for a strong female character, one who could rival Piggy, I don't think Annie Sue would be a good choice. Bring Spamela to the fore maybe. Or develope a new character to take on the role.
I think there are certain characters, and Annie Sue is very one of them, whose whole charaterisation is so much an extension of their original performer, that I think they should stay in the background, unless their original performer is available to do them. I don't mind them being present in non-speaking background roles but to bring them back as characters, well they just wouldn't be what they were and I think it would spoil them. Other characters in this cannon I think include: Floyd, and even Fozzie. I think it would have been better for Eric Jacobson to develop his own comedian character as a replacement for Fozzie. In a way although I didn't particularly take to Spamela, I did like the way they had tried to develop a new character to fill the role as Piggy's rival.
By all means examine characters who were very minor in the good old days, especially ones not specifically associated with any one performer, and see if they could be developed further. But I'd rather see The Muppets develop completely new characters than bring older ones out of retirement.
The only exception to this is Kermit, partly because he is such an icon, and largely because Steve Whitmire really does a good job with him. But other than that I think many of the older characters (and that includes Annie Sue) were of their time. Things have moved on since the days of The Muppet Show.