I'd not heard of people being taken off benzo's with phenobarbital before -- only the use of a long-acting benzo (eg. Valium). However, a quick google revealed that there is indeed some literature to support phenobarbital substitution as a withdrawal strategy.

Eg: http://www.ncbi.nlm.nih.gov/pubmed/1575069

The major bone I have with this strategy, in your case, is that you've just been through no small amount of trouble with these substances, first with gabapentin, and now with Klonopin. As such, I'm skeptical about introducing yet a THIRD medication which causes dependence, and from which in turn you'll have to be weaned after the substitution phase.

Furthermore, substitutions in and of themselves are not seamlesss, because different drugs have different properties. This is true even when substituting one benzo for another. After the Klonopin has been entirely removed and phenobarbital put in its place, you'd have to commence the gradual suspension of the phenobarbital.

waves