Sorry. You are wrong⦠
The Colonialās medical and scientific technology is sufficiently advanced that they would easily detect nano-machines in Cylon blood.
They clearly have CAT-type technology, DNA-typing, etc. Electron scanning microscopes must be routine to have this sort of stuff. Hell, they have FTL drives! Our own current tech can āseeā and manipulate individual atoms, so it is reasonable to assume Colonial tech is at least as advanced.
There is no conceivable (or even inconceivable) machine/nanobot/whatever which would be smaller than atom-size. For a machine to even function at the most basic level one would imagine it would have to comprise a level of complexity of a magnitude of at least thousands of atoms.
I keep returning to one of my very original hypotheses, from oh-so long ago, which met with deafening silence, slight disagreement, and only very occasional support at the time: there is effectively no difference between āhumansā and āCylonsā. Colonial technology could not separate them via DNA, microscopic analysis, etc. I suggested (and still largely do) that all humans are Cylons, that really Cylons are humans with certain genes āactivatedā. When activated, otherwise seeming-junk DNA turns on downloading capability, extra strength, projection, hidden programming, etc.