This part I have still not grasped due to lack of knowledge in this area. If this SCL puppet is isolated from the system, why would it affect a Puppetserver installation?
You will have to educate me more here. Right now this adds 12 gems to our build process which doesn’t feel like a lot of burden. I get that Facter would add more due to its more complex nature, Fedora does package this and it’s dependencies so we have something to look at.
How do you mean? When using just the installer users are digging into /opt/puppetlabs ?
I read this as adding an increase to our need to declare our dependencies explicitly and include them in the installer. This does add overhead but allows makes things clearer which isn’t necessarily a bad thing.
I would think this means that the foreman-installer can’t upgrade to the latest Ruby, not Foreman. Last I checked, we live in this world already 
Admittedly this one confuses me due to lack of knowledge. If I look at puppet-foreman, this is being tested against the puppet gem already. I would think that this would align us closer then.
Check out this comment RFC: Moving Foreman Proxy, Installer and NodeJS to SCLs - #10 by ehelms