I realize this post is slightly old, but wanted to give some feedback --
Keep in mind that FK on memory-optimized tables can only reference other memory-optimized tables.
The edition of SQL Server has no effect on the "redundancy" as you mentioned.
If your tables are created with DURABILITY = SCHEMA_ONLY, then after database restart (or server crash), the table is recreated, but none of the data that it contained exists.
If your tables are created with DURABILITY = SCHEMA_AND_DATA then after database restart (or server crash), the table is recreated, and ALL of the data that it contained exists. All durable memory-optimized data must be re-streamed from files to memory, and this can affect RTO.
For FCI failover, there is no difference in what I wrote - durable data must be re-streamed from storage to memory. But for Availability Groups, the data does not have to be re-streamed, because as REDO occurs on Secondary replicas, memory-optimized tables are updated. Whether or not the Secondary is readable makes no difference.
Also note that as of SQL 2016/SP1, you no longer have to use Enterprise edition to have memory-optimized data, but there are limits on how much you can have.
If interested, I have many posts on In-Memory OLTP at http://www.nedotter.com