Maybe using dongles or USB port the user can use regular keyboards as input device rather than buying a separate accessories.

Personally I like portable and small form factor device, but I guess larger screen make sense as well for legibility and ease of reading. However, be careful to not make the final design too bulky.

Thats pretty interesting, maybe the same method to make the external module hardware can be open up to developers for them to make their own unique accessories and modules.

Its has a unique design and stand out more than being a standard e-reader design form factor. It also gives room for developers to be creative with the buttons the same way the Playdate Console did to their unique crank mechanic.

Other avenue to explore for the handheld is maybe a smaller Gameboy Advance inspired handheld form factor that is portable and small with small E-Ink displays as buttons on the sides and one main E-Ink screen.

If the device would be in size of a small tablet, maybe it can fit buttons that have a small e-ink display in them that the developers can mess around for different situations on the games.

Is there a plan for built-in online game store like the Playdate Console? Or would the games run only from an SD Card like a retro old-school game cartridge?

“The Galaxy Is On Orion's Belt” - The Arquilian

For comparison most of the common MP3 that can be bought at 2001 like the Rio 600 can go about with about 32MB to 64MB of flash storage memory. So a first generation iPod can store half or all of the songs in those players in RAM.

That’s a pretty good reference.

The 48 KB version of the Sinclair ZX Spectrum cost £175 in 1982. Adjusted for inflation, that’s £597.14 or about £600 in 2023 which is close to the PS5 Pro’s price of £699.99.