Using "new threads" with seL4

Hello. In the course about seL4 in lecture 3a the advantages and disadvantages of threads and events are being discussed. The conclusion is that some kind of “new threads” should be researched which could be more performant and easier to use than current threads and events.

Of what nature are these new threads? There are two papers (1, 2) discussing implementing concurrency-optimal binary search trees. Are these examples of new threads?

I would like to implement such a binary search tree on top of seL4 to compare the performance and ease of use with an implementation of a BST using old threads. Has something similar been done before?

Here is the course about seL4 and the relevant slides.