There's a solution that we teach for this.
Ultimately a member's TCC website is only 1 website, with 1 brand and 1 sub-domain.
What we teach is for the coach to create what we call an "Umbrella Brand."
A great example of what we mean by "Umbrella Brand" is http://www.michaelport.com/. (Please note that he does NOT use TCC for his website. It's a custom website, but you'll get the idea.) The main home page lists each segment of his business. And when a visitor on his page clicks on one of the business segment, they're taken directly to that section of his website that addresses that aspect of his business.
For example, instead of just using my coaching company's name, "The Coaching Advantage" to brand my website, I would create an umbrella brand for "Melinda Cohan" (because I'm the common denominator of all segments of my businesses/niches) and under that umbrella brand I would include the different niches/businesses I'm involved in.
In your case, you would create your Coaches Console website Brand to be "Your Coach Name", so that all pages, color themes, graphics on the site are consistent with that umbrella brand. Then if, as an example, you would have 3 niches, you would create 3 separate, custom "Pages" on your website, one for each of your niches/businesses. Each custom page should would include the specific images, texts, etc., specific to each niche/business. That would allow you to redirect each of your external domain names to the niche specific page URL on your Console website. When a visitor arrives regarding business A, the visitor would see in the upper left corner the "Coach Name" brand, but on the specific page they're looking at they would see the info for Company A.
You could also create a generic "Welcome Page" for your "umbrella brand" that lists the different areas of your business. So that when visitors arrive to your welcome page, they sell all aspects of your business and can click to be taken to the custom page with the details about the business they're interested in.
If however, you are adamant about having separate websites for each niche, with distinct brands, each unique and different from the others, you would need to create different external websites and simply use your Coaches Console website as your back-end Private Client Portal to manage your clients and participants.