lazygardener:
I see woody plants as espaliers in the US. But give it a try
you are in the right climate that a espalier would work
like that.
Art

Salvias are very prunable, so it might work, but would it look right? I don't know the hybrid you mention, but S involucrata flowers on the tops of the stems and doesn't produce much in the way of side-shoots, in my climate at least, so would you lose all the flowers?

Puberula x karwinskii (the one from UC Berkeley) is a very tall sage, and weaving it through a fence will help with wind resistance.

As far as I know, puberula has subspecies status to involucrata. There is a distinct difference between the horticultural forms of available puberulas and involucratas.