Most medium Australian contractors enter cut-to-length processing through an excavator conversion rather than a purpose-built carrier, and the logic is sound. The expensive part — the carrier — is already owned and already earning, the capital committed is far lower, and the machine retains a deep resale market.
The head can also outlive the carrier. A well-chosen head transfers to a replacement excavator later, which protects the investment in a way that a purpose-built machine does not. Confirm hydraulic compatibility, control system interface and mounting before assuming it, because the electrical and control side is usually the constraint rather than the mechanical fit.
The trade-offs are real. Boom geometry, cooling, operator visibility and continuous-duty capability are all inferior to a purpose-built harvester, so production per hour will trail. In Australian summer conditions, hydraulic oil temperature rather than flow capability is usually what limits the combination — so confirm continuous flow at working temperature, not peak flow on a cool morning.
The decision threshold is annual paid harvesting hours. Above roughly 2,000 contracted hours, the purpose-built machine's specification earns its premium because the duty-cycle penalty compounds every shift. Below about 1,500, the conversion usually returns more.