Oh, your question just solved my idea, I noew re-structure for my blog, move niche's posts to niche's subdomain (eg: posts about Woodworking will move to https://wood.chebinhdan.com). Now its very clear for me and you:
- Create a new blogspot (mocbinhdan.blogspot.com)
- Add 3rd party subdomain to it: moc.chebinhdan.com (updating)
- Clone the template from main blog to sub-blog. Fix the menus items
- Create a new page on new blog: moc.chebinhdan.com/p/moc-binh-dan.html (landing page)
- Remove sidebar and hear for the landing page if has them
- In new blog: Setting > Search preferences > Custom ReDirect > set redirect from subdomain (moc.chebinhdan.com) to landing page
- In the old blog (www.chebinhdan.com) add the new Menu title > point to landing page URL or subdomain are the same.
Thats it. You could do the same with contac page. You could check my blog, I've just test with it (not fix the sub-blog menus jet, tomorrow)