Question: I just got a new work laptop. I would like to seamlessly switch my bluetooth devices (headphones, magic keyboard, touchpad) between work / personal Macs without complex repairing.

Has anyone solved this problem?

Ideally, I would love it if my bluetooth devices just paired with the computer docked into my dongle that connects to my monitor / power. Like if there was some kind of USB bluetooth controller that exposed my bluetooth devices as USB devices to whatever was connected to it, that would be awesome. But I haven’t found anything like that. I’m curious if people have different solutions?

It would also be ideal if this could be used for other bluetooth devices, ie seamlessly switch headphones...

Answer: 
I have a lightning cable connected to the hub that drives my external monitor. And connect my work or home laptops to my monitor. Then I can plug that lightning cable in to the magic keyboard and/or trackpad when I switch or when I need to charge the keyboard or trackpad. I don't switch all that often, so it is good enough.
Software KVM solution such as Synergy, Across, others... But you would need permission from Work to install the software on the Work MacBook Pro.

That would work for the KB/Mouse/Trackpad but for the bluetooth headphones they would need to support multiple devices as Allen said.

Your employer may not like the idea of a software KVM. Your mileage may vary, depends on the employers IT / IT Security departments.