Hello !
Your ideas aren't bad and I'd like to share my point of view.
Concerning your second point, I don't know if putting Duality on Steam would have a huge impact, but I saw that your major argument was to use Duality's modularity to attract more people. While I agree with you, the problem is that Duality is lacking of module. At the moment the actual package explorer/manager is fine because there aren't many plugins (but a sorting system would be nice).
That brings me to this point : your ideas are great to attract more people, but not to retain them. Currently, if you look at
Duality's wiki, it's empty compared to, say,
Libgdx's wiki. At the moment, if you want to do something, either you google it (but community is small, thus you won't get many results), or you look at the wiki (but there aren't many tutorials), or you ask the forum (again, small community, so you aren't guaranteed to have a quick reply), or you look at the samples, or you look at Duality's sourcecode.
As I did the last Ludum Dare with Duality, I can tell that I've been sometimes frustrated by this lack of tutorials (by the way using the google search of the forum is your best bet to get something

), and
by the lack of plugins that would have been nice to have. For example, managing animations was frustrating : I followed
the actual tutorial on the wiki, but it is flawed : each time I wanted to add an animation in my spritesheet using TexturePacker, it would mess with the indexes and I had to change every single number manually. So, why not make an editor plugin ? Welp too bad, no tutorial (which has been
requested many times in the forums). I tried to look at Duality's source code, but, no offense Adam, I only saw huge classes that I don't know how to read. Therefore, I abandonned this idea which made me lose quite a lot of time and did everything manually. Can you see the problem here ? No tutorials = No more sweet plugins for the community (unless you know how Duality functions, which is way out of my reach for now).
Wow I really sounded pessimistic in my last paragraph. However, Duality's community may be small, but not inactive. The project section of the forum regularly has new awesome projects. Plugins are being made, for example the
Input Mapping, whichcomes handy, or the new TileMap Plugin, which looks awesome.
To conclude, what we need at the moment are tutorials (e.g. "How to make an editor plugin") and more features (e.g. Adam already made the necessary work to make Duality multi-platform, we now need someone with too much free time to make it real), and new people will come here on their own.
Thanks for reading, and feel free to correct me if I'm wrong
(that wouldn't surprise me) !
