It would depend on the purpose. There are not many handhelds with this precise form factor, which is very special for some of us. If I could throw a 480x320 screen inside this and play slow-paced GBA RPGs in 2x zoom this would be awesome. And still cheaper than a Pi Zero W in a GBA SP case, and more convenient too (IMHO). A lot tidier for sure.
Doh, a man can dream
I'll soon be trying screens in an RG300; not like I can try many of them, but I'll take advantage of having to use some 320x240 & 480x320 screens for some other stuff and give them a try for this. I know I'll have to switch FW versions and keep my fingers crossed, but I'll do what I can, learn what I don't know and ask when in doubt.
With this form factor and input options I'd aim to GBA and down. Not to mention the JZ4725B. Maybe it's a too specific use case to get traction, but it sure can get some passion. Already has
I'll try fitting this device into my budget. Money-wise, it's not expensive. Time-wise... my time budget is complicated, to say the least, and I'll have to learn a lot. But I've got a multimeter!