  Silicon spin qubits stand out due to their very long coherence times,
compatibility with industrial fabrication, and prospect to integrate classical
control electronics. To achieve a truly scalable architecture, a coherent
mid-range link that moves the electrons between qubit registers has been
suggested to solve the signal fan-out problem. Here, we present a blueprint of
such a $\approx 10\,\mu$m long link, called a spin qubit shuttle, which is
based on connecting an array of gates into a small number of sets. To control
these sets, only a few voltage control lines are needed and the number of these
sets and thus the number of required control signals is independent of the
length of this link. We discuss two different operation modes for the spin
qubit shuttle: A qubit conveyor, i.e. a potential minimum that smoothly moves
laterally, and a bucket brigade, in which the electron is transported through a
series of tunnel-coupled quantum dots by adiabatic passage. We find the former
approach more promising considering a realistic Si/SiGe device including
potential disorder from the charged defects at the Si/SiO$_2$ layer, as well as
typical charge noise. Focusing on the qubit transfer fidelity in the conveyor
shuttling mode, we discuss in detail motional narrowing, the interplay between
orbital and valley excitation and relaxation in presence of $g$-factors that
depend on orbital and valley state of the electron, and effects from
spin-hotspots. We find that a transfer fidelity of 99.9 \% is feasible in
Si/SiGe at a speed of $\sim$10 m/s, if the average valley splitting and its
inhomogeneity stay within realistic bounds. Operation at low global magnetic
field $\approx 20$ mT and material engineering towards high valley splitting is
favourable for reaching high fidelities of transfer.
