"People should have the right to tinker with whatever they bought"

Absolutely. We've had so many on farm productivity gains by modifying our machinery. We've added curtains to our spreader to better spread lime, extended our machines axles to setup a CTF system and built our own wetting agent system for our seeder bar, just to name a few, all which required machinery/implement modification. In some cases, machinery manufacturers have come and looked at the modifications we've made to a machine (in the case of the spreader curtains), and then taken the idea and started building it into their machines by default.