Selecting only from multiple tables in a transaction
"consistent snapshot" and "repeatable reads" consistency seem to do exactly what you are asking, even mysqldump uses it with its --single-transaction option.

Because InnoDB implements MVCC, the DML running in parallel won't bother you when all the selects are non-locking (and from InnoDB tables).

The only way how to get "outside" is using SELECT .. FOR UPDATE which will be executed in the "read commited" isolation mode even when the transaction is set to "repeatable reads". But that should not be needed for extraction of data.