What I found out you are correct. Just don't delete the other account as you described.
You can create a separate account with sudo access but without a separate home folder
then add this user to the same group as the normal user and set it to use the same home folder with
sudo usermod -d /path/to/new/home
One account for normal usage and the other allowed to use sudo.
There is a way to do this by overriding the PAM (Pluggable Authentication Module)
settings for the sudo service. Do this at great risk to your machine - don't just copy and paste .
test test test! - before logging it out of terminal.