I think that given how long Spacedock (a.k.a. Probert Station) went toe-toe with the "entire" Federation fleet, and given that in addition it was evidently an integral component of Earth's planetary shielding, I'd imagine it must have some essential defensive components that are very difficult to replicate.
Plus it's fucking more massive than a shuttle by orders of magnitude and magnitudes. It can't just be "replicated."