And then there's the issue of the entire ecosystem of things you could program a scope to do that aren't even thought of by existing vendors.
Like what ?
From my Rigol:
* letting a user define an extra virtual channels they can use for math functions, offsets, etc (constants)
* adding highlight frequency in ffts
* adding the ability to anchor the trigger point left, center, or right - R&S has this
* porting over the math functions like e.g. micsig has - arbitrary functions so you can normalize waveforms, etc
* adding overrides, like adding 2.5x or 7.5x probe values so you can do tricky offsets (some other scopes have this in hardware)
I mean, whichever scope has large sales and open source will very, very quickly have the best bus decoding features out there.
Before going even more off topic, I will repeat some things said before elsewhere:
Scopes don't have unlimited memory and processing power. They rely on delicate interplay of hardware processing engine and software. Both will be limited and defined by actual chips used inside.
Large parts of rendered waveforms will be done in hardware (ASIC or FPGA) and then given to CPU to render overlays. Some traces will come from hardware some from CPU and they are mixed on same screen and scaled to look and feel like they are equal. All of that makes real, working, embedded scope, and that cannot be open sourced. It could, but would gain nothing. Nobody would do anything useful with it, because it is out of capability of heard to write something useful there. There are dozens of scopes that got reverse engineered to the point that it was known what it does and how hardware looks like.
None of them got nowhere. People managed to run Linux on it and play doom. None of them even got to the point acquire waveforms at all. None of them even got to point to even match functions that scopes got before they started "development".
What could be done would be PC scope like the Picoscope, the basic acquisition engine that does nothing than just sample data and gives it to PC for all processing. Then all of the scope functionality IS in software, and that would be closer to what could be managed. And indeed, there is a very, very clever guy Andrew Zonenberg doing just that. He is developing both acquisition hardware and software for PC. And software can (and does) work with many scopes, including effort to make it work with Siglent scopes.
Just to be clear, that is not classic scope though. It can manage few wfms/sec. As you go up the food chain, high end scopes are specialized for advanced analysis, not screen speed..
That being said, most of the stuff you enumerated here, SDS2000X+ already have, and some are visual user preferences, that might, or might not be interesting to all users.
But it is always nice to have (nice) discussion and hear clear examples and suggestions (instead of just "this bad..").
You never know, if possible and idea is good it might even get implemented..
To answer to you on RTB2000, I think it is a very confusing scope. It has some very nice features, but is limited (deliberately) in some very annoying ways. There is no search on any serial protocols except on CAN. Segmented memory is implemented as a "datasheet feature" it is not as powerful as it should be.
It is basically an Apple of scopes: expensive,fancy and visually polished, with many good features but also limited in many ways that are not obvious at first glance. And then you realize you could have bought Xiaomi phone with Android for much, much less money and still accomplish same things with it. Call, and SMS and read mails etc etc..
I really, really, would politely ask, if any of you want to discuss more on open source scopes, than a topic should be opened and we can discuss it there...