Is it reasonable to use ESP32 for a BT/WiFi?

I'm looking to add BT and maybe WiFi to my Arduino Mega. I see that the costs of the BT module is near the price if getting an ESP32 that has BT/WiFi built in...

So I was thinking that if I can just get the Arduino to communicate with the ESP32, then I can use it as a BT module, then when I'm done, I have a full ESP32 controller board with BT/WiFi built in and I can use that for a separate project.

Q. can you use an ESP32/BT/WiFi with an Arduino, similar to buying a BT module but having to figure out how to send/rec'v data between them?

You can communicate between the Mega and the ESP32 using Serial and have the ESP32 handle BT or WiFi (but not both at the same time)

You should also consider whether you need the Mega at all, but that depends on your application but you have not given any details

Given the trouble people appear to be having interfacing an atmega and an esp, I'd very much recommend dropping the arduino in the first place and just stick with the esp -which coincidentally turns out to be quite a capable device.