Well, I just discovered that there's a way to play games designed for Local Co-op only (such as Enter the Gungeon or Nuclear Throne) through the internet or over LAN with a friend. It's a fairly complicated process (they explain it
here), but given that it's technically possible, I'm definitely a lot more excited for the prospect of Local co-op for Starward Rogue. I hope you guys can add it in the future, I'd LOVEE to play with my friends.
Edit: Just tried it over LAN. It's actually not complicated at all and it seems to work great. I'm now very excited at the prospect of playing Starward Rogue "Local Multiplayer" over LAN with my friends.