This is one of the really cool things about Domino: it doesn’t care what OS it runs on.
Create a new server on the System i and cluster it with the Windows server. This will let you use AdminP to create replicas and you can get everything copied over pretty cleanly. You can then decommission the Windows server and update the notes.ini on the System i to match the other server’s name. Copy over the Windows server’s server.id and you should be pretty much set. Bring it up and delete the cluster. Just be sure to update DNS or change the IP address on the Windows server if you’re copying it to the System i.
That’s the cleanest way I have found to get servers moved to new hardware, regardless of the OS involved.
It is - I’ve done it a lot. Actually you don’t even need to cluster - you can just replicate with the new server. I’ve then swapped IPs and server.id’s and voila, both servers are up and running.