I wish there would be more opportunity for Mon-El to contribute to the DEO via his Prince-of-Daxam-ness. In 02x04 Survivors, he gave Kara intel on one of the gladiator aliens, and I think it’d be pretty cool to see something like that again.
Imagine… the DEO is trying to get information from an alien who keeps answering in obscure/obtuse ways. J’onn can tell psychically that this alien is trying to be helpful, but nobody understands what the alien is trying to say. Mon-El sees what’s happening and as is like, “That’s a Tralfamadorian. Their language is ordered by the architecture of the room. They never make sense if there’s two-way glass or a clear wall.”
Or, the DEO is contacted by an alien race, and they’re about to reply before Mon-El stops them. “That message is from the Pwegamites. Their culture is built on respect and honor. If you don’t carefully word your reply, they’ll view it as an insult, which could lead to full-on warfare.”
You know, just random things someone who was raised to handle political/intergalactic relations would know…