Why not keep it simple, make the body with just a hole to put a dowel through that is attached to the head. Bodies and heads stored in a bag seperately.
I know 2 people that use a battery operated mower and like the ease of use and no maintenance. I would suggest using a cordless weed wacker to knock down the heavy stuff and then mow.
Theese might work better than a plastic hull. https://www.ballisticproducts.com/MagTech-12ga-2-1_2-empty-brass-shotshells-for-reloading/productinfo/3921270/
https://www.researchgate.net/profile/Viktor-Astakhov/publication/284530412_Turning/links/5d4446494585153e5935c5aa/Turning.pdf
Printed 2011 full PDF, hope it is useful.