The mid implementation is not known yet. So, there is no way to tell what electronic drum kit would be useful for playing the internal voices of the AR with drums.
I suspect it will be kinda weird, where 4 voices will be on 1 channel and the other 4 voices will be on the next channel (this is kinda how the MachineDrum is). So, you would probably need a midi brain that can handle sending midi notes from pads to different channels.
It is also not currently known how the AR will respond to velocity. If there is a way to change what it effects, etc…
So, until a manual is released, you won’t know if the AR will work for what you want. If it’s not, you might look into a Nord Drum 2.
edit: Also, if you are planning on playing the internal sounds of the unit triggered from your drums, then the Octatrack is definitely NOT what you want. There are much better samplers, purpose-built for that sort of thing. The OT is about direct manipulation, not external triggering.