Why didn't Palpatine install a killswitch in Vader's armor or put him in a slave collar?

We know from erdiede's and spong's respective answers to the questions Why was Darth Vader given a downgraded version of General Grievous's mechanics? and Why is Darth Vader's body suit considered an upgrade to General Grievous? that Darth Vader was intentionally given armor with obsolete tech to slow the Sith progression and to make him less of a threat to Palpatine. But this seems like a half-measure when he could've hidden a killswitch or self-destruct option in the armor?

If he really wanted to go all the way he could have put Vader in one of these slave collars that were used by the Sith Empire. They apparently work against force users as well, given that Jaina Solo was forced to wear one during the Yuuzhan Vong War:

Sure, it's drastic and humiliating. But I wouldn't put it past the man who punishes Vader by removing his flesh to do that.