To me the biggest challenge of migrating to online teaching would have to be creating a collaborative virtual environment. In the online classes I have taught in the past, students liked the time flexibility and asynchronicity that a f2f class could not offer. This was a fact I failed to take into account when assigning my annotated bibliography group research project.
I naively thought that online students would possess enough self-motivation to cooperate independently with one another, and I offered all the toys available on Blackboard, such as wiki pages, file exchange, blogs, and group discussion boards. In the end, there were not enough such students, and the toys were seldom used.
That said, I would try migrating a multimodal assignment that evaluates online news outlets for bias and classifies them in a chart. If anyone is interested, check out these links:
In my f2f classes, this kind of big research project is assigned and groups are formed very early in the semester. The groups work together for other collaborative activities during the course, and as a result, form strong bonds.