Although OmiOS probably represents the safest bet
Tribblix in its"OmniTribblix" variant (based on Joyent's Illumos) supporting LX-branded Zones, is a very lightweight, stable (fixed releases including 3rd party software) and versatile alternative
Tribblix supports SPARC (ISO based on defunct OpenSXCE) and still maintains a i686 fork, in spite of the fact x86 support was removed from upstream Illumos
4 months ago