Sorry if I am being long winded –
To ultimately get 50 different IP’s for differnt IP’s but manage it centrally will be a really hard process even with investment
Every server has an IP address and that is fixed. Even when you sign up to a shared hosting plan you will have a maximum of 2 IP’s as they will place all there shared hosted sites on a bank of servers A-Z. And your site at Rackspace will be one of X on the same IP range
Generally speaking your hosting company will occasionaly move you to a different server when they have problems to ensure your site is kept live.
Whether you have a hosting company or different account set ups, ultimately it will take you the same time managemnt
I am not quite sure why you would really need to split up every single site.
I would suggest combing different options
Hosting Reseller – x 4 accounts dropping a few sites into each
Shared Hosting – for any sites that I did not want associated with the others.
If privacy is really important to you apart from hiding registration details, I would use differnt company names and a mail drop reference for the address, as ultimatley your payments would be going to one company which would not be on the domain
But it does seem great lengths to be going to.
One of the biggest advantages in splitting out sites for differnent IP’s can be SEO
For example I use a US hosting reseller and a UK hosting reseller and then some shared hosting plans – split between european server locations
Shared hosting for total privacy and country location of server so for my UK sites ranks highly in Goog UK, German site on german shared hosting for Goog DE etc…
the biggest advantage of the reseller account is you can try new sites and bin them if necessary instead of individual hosting for each. So really helps testing out as I am sure like most people you have some core sites and then a few that grab players here and there
I know its a very long way of saying mix and match but I know I would not remember where I had half my sites if split between 50 single hosting packages