Continuing the parent ...

It seems I digressed a lot, but while one can make very sophisticated models, the "upper limit" of a mod, and the ceiling of the modding community as a whole, really lies on:

* How one can extend the engine. But this makes sense only if one can do this, i.e. has the skill, time, and resource to do it. It's not just some arbitrary CRUD logic, it's bulks of assembly code compiled from poorly written sources (thankfully the compiler is also poor so not much optimization).

* How one can make the best use of the existing features of the engine in absurd ways.
For example, suppose I want a tank firing laser from the sky (think about Athena Cannon in Red Alert 3 https://www.youtube.com/watch?v=IbX7R3UYtzI), the engine doesn't offer such a feature. The solution is to set the Z component of the unit's "firing coordinate" to 65535 so it "looks like" firing from sky.

A more advanced example would be mimicing the sweeping laser of Colossus in Starcraft 2 (https://www.youtube.com/watch?v=u5YEI-_o5dQ), or laser of Future Tank/Giga Fortress in RA3. To do this, one can 1) Make a unit launch a V3 rocket, but make the rocket invisible; 2) Add a weapon to that unit, that automatically attacks the "rocket" it fires, make the weapon draws laser. Then as the "rocket" is approaching the target, the unit will attacking the rocket with laser, and as the rocket is moving, the laser will look to be sweeping. That's how you get this "BTS": https://www.moddb.com/mods/mklab/images/behind-the-scene

Surely this is a horrible hack and it'll break as soon as you have multiple Colossuses in a perimeter simultaneously - the laser weapon works by "filtering all rockets of a specific tag", but the tag can't be made specific to every "instance" of Colossus - there is just no such feature! They will just randomly pick a rocket fired by others and draw the laser and the whole stuff breaks up.

In reality, most people ends up in the later way because they can't do reverse engineering, there are many clever tricks just like the one above contrived by clever people. And even if you're working on the engine binary itself, it'll just be more difficult and time consuming to extract any non-trivial stuff from the huge sequence of instructions.
All these won't be necessary if the game is open sourced. I personally feel sorry for all these brilliant minds "wasted" on these useless shits. And that's exactly why I don't do modding anymore (maybe I'll pick it up again if this open source of Remastered turns out to be interesting enough).

However, despite the grim situation, some people that's working on workarounding the engine just lock their stuff for themselves, for their own mods. They're not sharing. This means newcomers can't leverage their existing program databases to do new work, can't get their own features integrated with others, and even redoing much of others work (no source code access). As a result, fewer people want to get into this business.

This is not an accident: TibSun/RA2 uses their own ".mix" archive for storing assets and some of the code. It kinda like plain tar, just concatenate all files together w/o compression. But the format is designed to be read only by the game. It allows the archive to store only hashes of the filenames, the actually filenames can be omitted in the archive. When the game requests for a certain file it just use hash to identify the file. We have a GPL tool for working with these files. But to protect unapproved reuse of assets and modding of the mod itself, some modders intentionally omit the filename in archives of the mod they distributes to make it incomprehensible for other humans. They also tinkered with the file header so it's only readable by the game and not by other tools.
This is, in fact, very reasonable, I'd say 60% people in the modding community are idiots, they're somewhat likely to just rip assets from other mods and use in their own mods without even crediting the original author. And sometimes it's just the author wants some "unique" stuff in his/her mod, and absolutely don't want others to use it under any term.

90% of the modding community don't know enough about free software, open source or GitHub (also reasonable since the modding community is just samples from ordinary players, and that's also why EA can't expect a proper "open source community"). They don't know how sharing stuff can make things much better. Of course it's their freedom to protect their work, and few people want to share stuff with idiots. I'm mostly with them for protecting assets. But as I said, the engine stuffs are different. These techs are critical for the future of the community, and are best shared as much as possible.
I know someone who did some work on the engine, and has been treating these work as the most closely guarded secret since then, and even becomes paranoid. He once consulted me about "how to protect these magic from being exposed to the public with his mod". Well technically you can do it! (of course only to some degree) But what's the point of doing this?

That's why I think the GPL license mandated on the Remastered source can really make the community much more healthy. Though I'm not very confidence about it - I also discussed with the paranoid guy above about GPL long before the Remastered. I think one can easily infer that if one don't get the point of free software and open source, then he is also not likely to know GPL at all, even if he knows GPL he still can't get the point of it, and will hold the most utilitarianism view towards open source: If I can use it, then take it for myself and hide it deep inside my mod, if I can't use it, find some workaround to use it. After all, it's not likely that EA will sue a non-profit modder for a minor licence violation ...

Edit: Fix the typesetting