What should be the path of execution?
It seems, the phone is not able to perform a de-auth itself.
So the phone should connect via BLE to the Flipper, which connects back to the phone, got anyhow access to the WiFi chipset and perform a de-auth attack? Plus the variations of chips.
Sounds not like a suitable solution to me.
Just search for Nethunter and get a feeling about how much mobile phones needs an OTG cable plus USB WLAN Card, to perform what you have in mind.
The reason why we need a special board is, because the Flipper itself doesn’t have WiFi. The advantage is direct access to the dedicated chip.