Something being a 'bodge' is someone's opinion - fitting an inline thermostat has been proven as a worthwhile cost-effective way to fix a common problem.
Just the same as soldering the under-seat connectors, using silicone to re-seal rear light clusters and fitting HID headlights to halogen projector units, some will always feel the inline thermostat is a bodge, and they're entitled to their opinion.
If the inline modification didn't exist, I'd bet less than 10% of people with an early-opening thermostat would do the proper job when they got a quote for the work - it's not a simple job.