The only way the absolute anonymity can be secured so absolute confidential meetings can be held is on a USA military base used for such purposes where the security of road access and air access is controlled.
There is no reason to meet with the Whistleblower if he/she is unable to come forward to testify. Every answer would have to be investigated further to find the truth the Whistleblower answered. In other words, a single source is questionably accurate without additional evidence.
The public hearings today are the work of the US House Intelligence Committee that has VALIDATED the Whistleblower facts in the reporting of a four-page document. The TRUTH is before the USA public today and in the weeks to come.