I remember when the Nintendo DS came out I thought it was a weird upgrade compared to the GBA. The dual screens it had made little sense to me, and while I never owned one the idea seemed distracting. But now that I’m playing the Castlevania Dominus Collection I can actually see where it would be beneficial, especially since I run a dual monitor setup on my main PC.
It would be pretty cool if the Steam Deck had an option for adding a second screen through the USB-C port. Yes, there are unofficial hacks that toy with the idea, but if Valve or some company started making them I would totally consider it.
Bonus if it doubles as a Power Bank.