You will not escape "approval". Eventually, everyone will be "approved" one way or another and be handed a secure ID with biometrics to scan by either working agents or automated portals. That is the point to all this. We as a nation have been very resistant to a National ID card with biometrics. This is how they are going about it, bit by bit.
I believe you're correct. Real ID, TWIC, Registered Traveler, Global Entry, HSPD-12, Military ID, RFID passport, etc. etc. are all moves to force a national ID. With the ability to completely revoke your rights for a single criminal infraction (think "one strike and you're out"... you can't even get a Global Entry or Nexus card from CBP if there is ANY criminal infraction on your record, no matter how long in the past and no matter if expunged).
Won't be long before such an ID is required for any purchase you make.
Recall that Chertoff said that an ID has to be "Real ID compliant" to permit it to be used to enter any government facility. The intent was to force states to adopt the Federal National ID standard
My hope is that when you get vetted and carded through one program, that it', you're now "approved" for all the programs. I'd be good with that. If I have to get a different one for each program, I'll be annoyed.
Not likely. Too much turf. TSA won't even accept a military ID or an HSPD-12 compliant government employee ID to allow access past a checkpoint. The list is so short that some TSA screeners have been playing a game called "ID Bingo", where they keep score of each type of "permitted" ID that they see.... that's how short the list is.
Even within one agency there is no commonality. For CBP, for example, a Global Entry card can't be used in place of Nexus and neither can be used in place of Sentri - and vice-versa. Even though you can
apply for each card separately, and even though you can be approved for a different card based on the first background check, you still have to go through separate processes, pay separate fees, and go through separate interviews.
The agencies are more worried about "turf", so there will essentially never be commonality.
Just look at the security clearance process for the Feds. DOD clearances are different than FBI, are different than NRC, and often involve some reinvestigation if you want to move from one clearance to another.