We don’t have the capacity to implement all the features users ask for, at least not without additional contributors or waiting a long time. So it’s better to implement it as a bot.

The cleanest solution seems to be the one described in my previous comment, so you get an archived community with all the original content, correct usernames etc. And make a new community for new posts. Or have the bot create new posts and comments with the same content, and credit the author in markdown body. But that seems like a worse solution in many ways.

Many of these are already implemented in Lemmy, others are too controversial and wont be added (such as karma).

We are currently preparing the 1.0 release which will have lots of major new features, such as private communities, multi-communities and much more. Although 0.19 is also getting constant updates with smaller improvements, for example 0.19.11.

Can you say which mod tools Piefed has that are missing from Lemmy?

Im not familiar with Wikidata, but with enough development time it could probably also be recreated as a Fediverse project.