SQL Server AG in primary site with separate WSFC AG in secondary site
1.Can a separate AG be a 'recipient' (restore target) of Log Shipping? In other words, can I have the primary server in a separate Availability Group be applying log backups (from log shipping) and when ready to cut over to this secondary AG, issue a RESTORE BACKUP WITH RECOVERY?


No, databases involved in an availability cannot be restored or recovered unless first removed from the availability group. You can log ship to a database NOT in an availability group, however, just fine.


  2.Ideally, it would be preferable to be able to more easily 'fail back' to the primary site. If we had a WSFC spanning both sites and the same AG on said cluster, I gather this would be far easier to accomplish. Network latency will be a concern.


All databases that belong to an AG must exist in side the SAME WSFC thus it would have to be "spanned". If network latency is a concern, work with your networking team to have dedicated bandwidth and QoS rules to make sure your traffic and the cluster traffic is getting through on time. Watch how often large bursts of log are generated, like rebuilding a very large index, and try to mitigate this as much as possible.