The only issue with the tablet design is you need the screen to be at least 10" in size for minimal bezel (there is a 10.5" FW mini tablet project here that does exactly that). And for some that screen size might be already too big for a gaming handheld.
I find the ideal screen size to be 7" to 8" though that would add a lot of bezel to the left and right. It’s all due to the dimensions of the mainboard. It’s not a square-ish “half-size” form factor like many of the handheld PCBs are. Which is also why the FW battery in the tablet needs to be stacked on top in order for it to fit in the case.