I once had a OpenWrt device corrupt the filesystem used on the extroot USB drive. It virtually ‘bricked’ the device… & I wasted, I feel, too much time repairing w/ a replacement drive.
This was back in the ‘bad old days’, somewhere around 2014, when most consumer routers only had 16MB of flash storage; forcing one to use extroot if wanting to do anything advanced. That’s not the case anymore! The Slate AX, Slate Plus both feature 128MB flash storage. I have a Slate AX. Its 128MB has 87.78MB used by the system. 41.12MB is still available after using a mere 2.11MB for some additional apps I optionally installed.
The Beryl AX has 256MB total.
I think quite a lot could be done w/ even 41.12MB considering the functions already provided ‘out of the box’ with the GL GUI (eg: repeater mode).
EDIT: Also, for you consideration, you might be interested in the results of @swissarmyknife’s testing of streaming three, yes three, simultaneous 1080p videos using the stock/built-in capabilities of his Beryl AX with a flash drive connected to its USB 3.0 port!:
Something to think about.