i think you hit the nail on the head, so to speak. I have tried to connect to various modern Boot-to-BASIC machines, and each time there has been something that halted progress. Maybe the common factor is me. I certainly have limitations when it comes to software development, even though I used to be employed as a software developer.
I'm probably trying to re-create that first experience when you got your shiny new computer and you needed to learn how to use it. I certainly enjoy that aspect of retro-computing.
Partly, I was always anticipating that if the computer hardware was simple enough, then "kids" could build their own computer...I could run a holiday program or something, and kids could go home with their own Boot-to-BASIC computer.
I am currently messing with the PicoMite VGA. The software looks very solid, and the hardware is affordable, but it is flexible to the point of useless. Unless they standardize on some of the interfaces a bit more, no one will want to develop hardware or software for it because it keeps changing. At the moment they are discussing what type of joysticks to support.
I'm trying to make the Tauon PC-1/Raspberry Pi 400 version of the PicoMite VGA, which is not as easy as it sounds. It uses a PS/2 keyboard, and they are not so easy to buy new anymore, specially ones that are small enough to go into a 3D printed case.
Anyway, I keep ticking away at it. I haven't given up on the idea of implementing the same for the BASIC Engine. The latest V88 tv box I bought showed me that you can get a working platform very cheaply. The all-in-one BASIC Engine PC is planned to be build around a commonly available cheap mechanical keyboard. Something like an AJAZZ AK33. The problem is, with BASIC Engine supporting USB, you are better to mount the main board on the monitor and use a wireless USB keyboard. There's not a lot of point in making an all-in-one keyboard computer like the old days.