The iPad leaves all mail on the server unless you specifically tell it to delete that email. You can remove and re-add the account on the iPad as often as you like without any problems. I do this all the time when I am experimenting with various calendar and contact syncing issues.
If you Hotmail account is working properly on the iPad, there is no reason why you would need to remove it, unless you have another method of getting the mail that you prefer.
And you can have both your GMail and Hotmail go to the iPad at the same time. It will work just fine. Just add the other account. When they are both on the iPad you can view all you mail in the Universal Inbox, or view just the account you want by choosing it's mailbox. Just tap the MailBox button at the top of the list view to go back and see what mailboxes or accounts are available for viewing.
The only catch is switching between the mail address/server you want your sent mail to be from. It will automatically send from what ever account your are viewing, unless you are looking at the Universal Inbox (called All Inboxes on the iPad). In that case it will send form the account you have set up as default in Settings >> Mail, Contacts, Calendars.