I can’t take your OS seriously. Unless it’s called Rockolixi Ultra, it won’t be any good. You’d be better off spending three more months and building the Ultra version straight away. That will make much more sense. Maybe you need a bit more megalomania in your mapping.
And you should definitely encourage other developers to start building apps for your new operating system, even if you don’t know how to get started yourself.
I like others here wonder where you’re getting “16 MB” from. zeptoforth fits in the 520 KiB of the RP2350 perfectly fine with multitasking, FAT32 filesystem support, an IPv4 or IPv6 stack, NTP support, and an RGB332 320x320 framebuffer. It fits even better if you ditch the framebuffer and use the text-only version (but frankly I have only had to resort to that on the RP2040, which does not leave much RAM left after the framebuffer, and which cannot fit both the framebuffer and the IP stack in RAM at the same time).
Even with your visions of an app store, they could be implemented simply by setting up an HTTP server somewhere (implementing a simple HTTP client should not be a problem), downloading source code with it, implementing a scheme of verifying signing of downloaded files (in the place of implementing HTTPS per se), and saving the source code into files in a file somewhere to be compiled later as needed. All of this is possible within zeptoforth (even though I am personally skeptical of app stores, part of why there is no zeptoforth app store).
Yes, you can’t ditch your laptop with it, but even with a Luckfox Lyra you won’t be able to ditch your laptop with it anyways, considering that with a modern web browser you can fit approximately one web page in all of the Luckfox Lyra’s RAM at a time, and that is if you are using it for nothing else simultaneously. (Seriously, look at the people who have tried to run Firefox on the Luckfox Lyra.)
Just take a look at some of the code used for this baremetal example for a similar Rockchip. If you still think you have the necessary skills and time for doing this all on your own, by all means go and do it.