Is there a downside?
Not really, i think. We have the resources, and being an admin isn't too time consuming; surely we can make time for an extra instance.
Would this be in addition to lemmy or a replacement?
Addition
If it is in addition to, is that the permanent plan, would this be working toward an eventual switch-over?
Probably not. There would be way too many potential issues and it's risky.
I should probably try piefed a bit so I understand it a bit better, but it's just a different Lemmy basically, right? Does it federate with existing Lemmy?
Yep. Try https://quokk.au/ (anarchist instance, too!) which is basically the closest thing we have right now