  As it has been demonstrated that trapped ion systems have unmatched
long-lived quantum-bit (qubit) coherence and can support high-fidelity quantum
manipulations, how to scale up the system size becomes an inevitable task for
practical purposes. In this work, we theoretically analyse the physical
limitation of scalability with a trapped ion array, and propose a feasible
scheme of architecture that in principle allows an arbitrary number of ion
qubits, for which the overhead only scales linearly with the system size. This
scheme relies on the combined ideas of a trap architecture of tunable size,
stabilisation of an ion crystal by optical tweezers, and continuous sympathetic
cooling without touching the stored information. We demonstrate that
illumination of optical tweezers modifies the motional spectrum by effectively
pinning the ions, lifting the frequencies of the motional ground modes. By
doing so, we make the structure of the array less vulnerable from thermal
excitations, and suppress the the position fluctuations to insure faithful gate
operations. Finally, we also explore the local behaviour of cooling when a
sub-array is isolated by optical tweezers from other parts of the crystal.
