Just the opposite. Both Firefox and Chrome's discussion of pipelining claim that "unknown" MITM software is why they didn't turn on pipelining. Nobody knows what this software is (could be malware). But whatever this mystery software is can't look inside SSL, so pipelining in SSL was just as doable as inventing SPDY.

If Google hadn't pushed SPDY then pipelining was going to happen, and the unknown bad software would have been fixed or blacklisted. Android was using pipelining for years in Browser until Google replaced it with SPDY. Mobile Safari has been using pipelining since 2013 (probably why it wins the mobile page load time benchmarks). Pipelining works.

Yes, some endpoints could be buggy, for instance IIS 4 (in Windows NT 4) was blacklisted in Firefox. Introducing a new, more complicated protocol just because of 10 year old outdated software is not a great way to solve problems.