Apart from the usual myth and legends that are still hit and miss about Pleuros and Maruloides being put in comms with big enough fishes, I cannot think of any channa species that can live in a comm once maturity hits.
Given the tank mates you want, only very few fit the requirements (most being sub-tropical), and apart from the two I cited above, you're down to a list of cold-blooded killers (Micropeltes, etc).
If the plat you saw are the ones that hit my wholesaler about a month ago, then they're Argus. If I remember correctly, that is the species that got the ban installed in the US and Canada, because it is one of the few that can outlive the colder waters up north, being native from Russia. Needless to say, they changed the ecosystem of the lakes and rivers to a point of no return for a reason. They are awful. If your Arowanas don't eat them when juvie, they'll return the favor once they hit 30'+.
As for the two only possible choices in my opinion, they're still hit and miss, mostly miss. Once mature, you are going for a gamble on whether it'll kill everything, and I am not sure I would gamble with Aros and Rays.
In truth, I have not heard of anyone trying it with Rays, so it could work, but I don't see why it would be any different than other fishes, I know my aurantis didn't like my hystrix even for the short time they were in the comm before being moved.