If iFixit starts selling steamdeck motherboards, can you buy just a motherboard and make a console-only version? Same motherboard, just no screen, battery, buttons.
And a SSD I guess.
Alternative question: Do you want steam to offer a console only version? Same motherboard, just no screen or battery.
honestly the steam controller's killer feature for me isn't even the touchpads -- it's the multiple-profile support. "oh, you want to connect to your PC for a bit, then reconnect to your console later? sure, just hold select during startup, I'll remember your last 2 bluetooth connections."
An RX 6600 paired with a Ryzen 5600 would blow the Deck out of the water (3-4x depending on the measurement) for a very similar cost to a mid-range Deck.
those two parts are 330€ new for me right now.
I'd still need:
a Mainboard, AM4 starts at 50€
RAM, 16GB for ~25€
Power Supply, 20-50€
ssd 10-30€
starting at 435€
Actually, that seems reasonably competetive with the 64gb version (420€), depending on the other parts you choose (I'd not want to completely cheap out on Power Supply or Storage, so give that ~20€ more each).