has anyone here ever created their own custom log in page for NetSuite?

I've seen custom/branded login pages for suitelets. What is your purpose? Having company branding? If so you might consider SAML. Then you can use a product like Office365, OKTA, OneLogin, etc to centralize your logins to all products and brand the page.

We do multiple deployments and changes to the environment. We usually needs all users out of netsuite during those times. I was thinking of using our own login page to also alert users or put up messages to prevent them from logging in. Just a thought

I was able to create it I'm can also disable the email address and password inputs to completely block users from signing in