Homepage Domain like blogger.com & blogs domain like blogspot.com

Hi - I've searched a lot and could not find the right answer that's why I am posting here.

I want the homepage domain to be separate from blogs domain.

For excample blogspot.com is my current domain with all 3000 blogs and now I purchased blogger.com and want to rename my brand. I want all new blog registration to happen on blogger.com but the domains for new blogs still stay blogspot.com.

So anyone register a blog on blogger.com, his blog should be created on blogspot.com.

Is there any way we can do it here on wpmu?