Frankly, my experience on mainframes is that UNIX is a stronghold there for a reason. I'd be far more interested in this ecosystem opening up by having strong mainframe vendor support for running Illumos and/or FreeBSD, and less concerned with running Linux. Among other things, Zones are more useful than lxc, and in this type of environment you often need strong kernel support for specialized high-speed interconnects and real-time operations, which Linux only has experimental support for but is integrated well in the UNIX world. I love Linux and what it's done for the world, but UNIX isn't dead for a reason, there are still many things it is superior at.