Is any SISO controllable and observable system dynamically passifiable and/or L2-stabilizable?

A passivating control architecture for SISO linear systems, comprising dynamic feedback and feedforward, is proposed. The approach - essentially without any restriction and by relying only on input/output measurements - provides a closed-loop system that is passive from a new control input to a modified output. The result is achieved by arbitrarily assigning the relative degree and the location of poles and zeros on the complex plane of the interconnected system in a systematic way. It is also shown that similar ideas can be employed to enforce a desired, arbitrarily small, L2-gain from an unknown disturbance input to a modified output, while preserving the corresponding gain from the control input to the same output. The paper is concluded with applications and further discussions on the results, which include constructions towards the adaptive control of non-minimum phase systems.