Right, that finally makes sense!
Create a customer group - called it squeezed (!). Edit the default customer group and set it so that no categories are displayed. Edit the squeezed group, and set it so that they can see everything, and check teh box that says "All new customers should be added to this group"
Copy /templates/_master/default.html into /template/YOUR_TEMPLATE/default.html
Delete all the panels that you do not need - newproducts, featured products, sidecart, sideategorylist, etc, etc, etc. You just want a shell. Then stick in your marketing info and copy the create account stuff to the bottom so people can create their account and log in to see things.
<form action="%%GLOBAL_ShopPath%%/login.php?action=save_new_account" method="post" onsubmit="return check_create_account_form()" class="PL20">
<div class="FormContainer HorizontalFormContainer">
<h3>%%LNG_PersonalDetails%%</h3><p />
<p>%%LNG_CreateAccountPersonalIntro%%</p>
<dl style="padding-bottom:10px;">
%%GLOBAL_CreateAccountEmailPassword%%
</dl>
<h3>%%LNG_ShippingDetails%%</h3><p />
<p>%%LNG_CreateAccountShippingIntro%%</p>
<dl>
%%GLOBAL_CreateAccountDetails%%
</dl>
<p class="Submit">
<br /><input type="submit" value="%%GLOBAL_CreateAccountButtonText%%" style="padding:2px 10px 2px 10px;" />
</p>
</div>
</form>
%%Panel.CreateAccountJavaScript%%
That should work, or need tweaking.
I have to say, as per Painstik, this is terrible idea for SEO (google won't see your site, people can't link, etc).
Also getting shirty because people have never come across a word you're using isn't productive...