Capsids are the exteriors of viruses (think the dodecahedron-like outside of T2 phage) They are made of highly repetitive protein. I think i read that many virueses actually produce large quantities of unfilled capsids.
siRNA drugs effect many cellular processes.
make the exteriors of viruses out
of siRNA, then have endoenzymes cleave them to the preferred functional length. Improving that slightly, alternate the usual structural proteins with siRNA so they are still structural, then have enzymes already at the cell or tissue divide them to produce big amounts of siRNA at any infected cell. The thing is that some of the loaded capsid viruses continue at the body with low virulence, spreading the siRNA to more and more places throughout the body, dosing as much of the body as possible.
completely different than CRISPR, although I tried to think of something simpler than CRISPR that could be a drug, as well as spread everywhere. custom enzymatically activated capsids could possibly do that.