I really like to design around the limitations of a given engine because I see it as an additional challenge and it yields a special satisfaction that is attractive in itself.
This statement would be true if you were modding, but in fact you're only working around the limitations of the map editor. The engine itself has various avenues for customization, but most of these possibilities are unavailable outside of modding as the editors only support the most basic forms of modification such as unit stats and names.
The limitations are entirely based on the (wildly) incomplete status of the tool you were provided with, while the framework allows for much more (as limited as it may still be). Honestly, there's simply no excuse when much better tools are freely at your disposal.
I personally enjoy working around certain limitations as well, but they must be inherent to the framework itself, or self-imposed if I wished for a challenge or exercise to test myself with. In the context of productive work, I fail to see the satisfaction (or even significance) when limited by incomplete or broken equipment. Relief, maybe.
[...]though I think in the past Andrea said that it's not interesting to him due to how the campaign would have a higher bar of entry/would be unplayable without downloading extra stuff
The user is already "downloading extra stuff" by virtue of downloading the map files from the internet. The only thing would be like Farty's installer in the case of non-SCR mods, but that's a one-time setup. The mod is already included in the package and only entails clicking a different icon than the stock BW exe, so all concerns about "accessibility" are absurd, and anyone who expresses reluctance to modding based on this is merely looking for justification to being derelict in the work that they do.
It's fine if they're genuinely not interested, but I can't accept any reason other than learning disabilities or laziness, or just outright ignorance that modding was a possibility. Although custom AI is the absolute minimum requirement for a worthwhile mission, I could still respect the efforts of someone with disabilities. There is certainly no merit in being lazy.
It is actually pretty hard to do campaign integration because of the way mission sound files are handled and packaged. You basically need to merge the SCX files with the mpq. Indeed I'm not willing to do this, it's just too hard for me.
I don't know what you're talking about. SCX files are themselves MPQ archives. When replacing the missions from the campaign menu, you basically treat your mod MPQ as a single larger SCX file: You import the sound files and the map CHK files into your mod MPQ, and simply have the strings used by the "play wav" triggers point to the correct MPQ path (as they do with scmd2's "virtual sounds"). Am I missing something?