Using MySQL InnoDB as an Archive
I would be very tempted to store in a no-SQL data store, like Mongo or Couch.  Writes are incredibly fast, scales well, etc.

You might even archive in a mongo collection, then store "processed" results in an RDBMS, which you can then query very quickly with SQL.

To stay in MySQL, you're looking at some sort of partitioning scheme to get this to scale at all.