we (the Hamburg Bit-Bots) also investigated this idea a few years back. There were multiple issues that we had:
1. The PWM servos we found were not strong enough (can you provide a link to the one you want to use?)
2. Most PWM servos can't be turned full 360° (I think due to using a potentiometer instead of a hall sensor for sensing the position)
3. It is actually some work required to make them daisy-chainable like the Dynamixel servos.
A PhD student from Berlin called Matthias Kubisch did some work on this while he created a 4-legged robot. He build a electric board that you can add to a PWM servo and control it via an RS485 bus. Not using the Dynamixel protocol, but reprogramming the firmware a bit to use another protocol is easy.
You can find more resources here:
Talk (english translation) - https://www.youtube.com/watch?v=UACttkydAfU
Github - https://github.com/suprememachines/sensorimotor
There are some things you might want to improve on this project. Especially, that the bus control only works with 1MBaud if I remember correctly.
I can also recommend to read the paper that we presented on the last RoboCup about communication with Dynamixel protocol https://robocup.informatik.uni-hamburg.de/wp-content/uploads/2019/06/dxl_paper-4.pdf