No revisit is necessary after 8 years. The structural issues with linux on the mainframe are exactly that- structural. How aboout this- go into real mainframe shops in mainframe-committed businesses like insurance, transit reservations, banking, and so on, and find out what the core business transaction systems run on. It won't be linux, and for manifold good reasons, mostly related to RAS. Linux has nothing even remotely resembling the abilities in Parallel Sysplex(zOS), but there's no need to escalate to that- even the most basic device error recovery management in a mainframe operating system is better handled than in Linux.
And by the way, the assumption that with the progression of years comes inherent improvement in technology is by no means a certainty, especially in computing. Ask someone who knows anything about Keykos whether today's operating systems have incorporated even half the concepts they got right. Oh wait- let me not forget- Keykos and many other earlier operating systems aren't covered in a typical CS operating systems course, but that must be because the 'experts' have deemed them irrelevant. The same 'experts' ignore TPF/zTPF as well, which have been happily doing transit reservation systems for over 40 years. So much for progress inherent in the march of years.