[CentOS] Crazy thought about upgrading to new major release

I have older systems out there that work fine, just for what ever reason
would be great to upgrade from a C5 -> C7 (due to no longer supported) or
C6 > C7 (for updated packages).

Sounds like the upgrade tool is not quite an option...
I was thinking...

What would be wrong with any "easy" script that did the following:

1) Removed all packages with the --justdb option.
2) Import the RPM-GPG-KEY-CentOS-7
3) install the centos-release-7.3.1611 ... rpm
4) yum -y upgrade
5) yum groupinstall "GNOME Desktop"   (for example)

and reboot of course.

Does that have any chance or working and be valid?

Thanks,

Jerry