I'm thinking that the "protects from professional retaliation" is the bigger issue for most. Look at what they're doing to Presidents. Imagine what they would do to cubicle staff.
I'm thinking the big issue for most Americans is to save our country from the entrenched disciples of deceit in criminal deep state. Things like this can destroy a country ya know, and they were well on their way to doing just exactly that, prior to the Trump era.
I would guess if a few came forward with crippling evidence which effectively derailed criminal deep state, but would possibly jeopardize their careers, they'd be seen as true heroes and they'd likely be offered other jobs, be taken care of, book deals, movies etc., who knows. Btw Trump don't forget those who back him and I'm very confident Trump would not turn his back on them.
Let ask you, if you had no protections or guarantees and you were sitting on evidence that would cripple criminal deep state, blow it wide open, but doing so would jeopardize your job if ya came forward, would you remain quite?
FWIW, I see this as much more important than a few losing their jobs.
And before ya answer remember, even with subpoenas/protections in place, they could still attempt to kill a whistle blower regardless of protections/guarantees.
In any event, as I mention early, if subpoenas are the only way to get them to talk, so be it. Getting the subpoenas/guarantees out, shouldn't take long at all.