I tried doing this via editing the URL, but it doesn't seem to work. Is this something that can be done somehow? There's gotta be a way other than sharing the password...

If not feasible, possibly add the last few remaining rank 1 admin options to the feature access list?

Nope. For security reasons, there is one rank 1 account.

Rank 1 = Absolute Admin/Owner of the site.

You can make alternative ranks that have access to most of the features, or you can edit an account and mark it as "Full Admin Privileges", but giving more than one account Rank 1 access has only proven to be a problem in the past.