Allyn Gibson wrote:
But, Cutter John, Doctor Who is a series that is defined by change. The actors change. The writers change. The look and feel of the series change. Justin Richards went as far as to say of Doctor Who that "neither the Doctor nor the TARDIS are strictly speaking necessary."
1. Doctor Who
has been historically defined by change, but this does not mean that radical change will be successful today.
2. Even if major change is helpful, that doesn't mean that several major changes all at once
won't be too much for the audience.
After all, nuWho has been fairly stable since David Tennant assumed the role; there is the possibility that too much major change might hurt the series today and lead to its cancellation.
I'm not saying it's likely -- I'm just saying, bear in mind that what worked 20 years ago is not guaranteed to work today.