Remove account without affecting the data
The way I see it, the only problem you have is losing your contacts if you sign out of your Google Account.

First of all, your contacts on your Google Account can be accessed on 
Google Contacts, so signing out of your Google Account on your phone doesn't necessarily mean losing all of your contacts on that account.

Secondly, transferring contacts from one Gmail account to another is fairly easy, and you can find a step by step guide on how to do so Here