I remember reading someone's argument against undirected evolution which used the Krebs Cycle (an essential and extremely complex chemical process within photosynthesis) as an example of unavoidable interdependent equilibrium. A partial Krebs Cycle does nothing beneficial for an organism. For that author - a molecular biologist - it therefore strained credulity that untold generations of organisms with worse-than-useless bits and pieces of the future Krebs Cycles got selected to reproduce until the necessary sub-components randomly combined into the functional process.

So . . . to answer my initial question . . . silicon-based life is plausible, but not for the reasoning used in the introduction to Uller Uprising.