Have considered using two identical views on top of each other. Only one is visible. One has a password reveal, the other doesn't.
You can then control which one you want to show at what time. When focus is lost, copy text to the alternative view.
Note, I did look at the source code for B4XFloatTextfield (Anywhere, Internal library, XUI View.B4XLib). The internal switch to determine reveal or hide occurs in multiple places, so a simple modification is not in the cards.
I do see the need for this effect. After leaving a field, it is reassuring that the password is hidden again. It also let's you force one-time entry of password.