That's what @Shida envisioned as well, but as you probably understand, it requires us to rewrite all of our code to make everything extensible. Probably rewriting some of our own functionality as plugins as well, kinda like Flarum's design.
Also, I don' think it's possible to just copy paste your code into our codebase and call it a day (given you've given us permission), since we should use more native ways to integrate the functionality. As I understand the PowerPack, there are limitations you have to work around since you only have access to the global DYNALIST object. In any case, both the UI and the actual code needs to be rewritten before merging the code.
Re: sorting, we're thinking of making it a menu option with shortcut, rather than using tags.
Re: Kanban style, we actually have a different idea about how to implement it. What you did is more like what we call the "split screen" feature, which allow you to work on different documents at once. iframe is probably the easiest way, but it's heavy on RAM usage and such. The Kanban view we imagined displays children of the current list as panes, and the children's children as cards in a pane, like Trello. In the Kanban view, you can zoom in as well to reveal the children of the grandchildren of the current list... not sure if that makes sense, but it still displays a single document/list.
@Piotr: congrats on making the most popular topic in the entire forum, by the way!