I can recommend two options:
. Modify the MonoX's default profile rewrite rule in web.config to point towards your own profile page.
In your custom project you need to inherit the BlogPostView control and override its ParseBlogPostTemplateTags method. This is where you could insert your custom logic, you need to change change the AuthorProfile tag contents, ex:
"<# AuthorProfile #>"
Inherit the BlogContainer control and copy the default markup. Change the path of the BlogPostView to point towards your custom control.
Inherit Blog.aspx and copy the default markup. Change the path of the BlogContainer to point towards your custom control.
Change web.config URL rewriting rules to point towards your custom Blog page.