Save files work both ways. For example, in Ocarina of Time (and almost every single other Zelda game), regardless of when or where you save in a temple, the next time you load up that file Link will spawn at the temples entrance. This is what I expect to happen to 'turned off' charges. No stopping it mid-way and then being able to pick up exactly where you left off, thus still allowing you to do exactly what I'm against, which is turn anything into a prep when it shouldn't have been. This still functions entirely like multiprepping.
Also, I swore we covered that stacking abilities doesn't naturally count as a charge unless it takes a full turn. Like, me combining two barriers doesnt neccessarily make it a prepped barrier, just a well fortified one. As for your time paradox 'empowering' preps, I'm not sure what you mean. If you mean that the time paradox should skip a +1 to a +2 without actually taking the turns to mature it that far then I'd be against it. Since that would directly correlate time to power again, which this prep system does not do.
Edit: to put the nail in the coffin of the 'surprise' prep argument, if you could suddenly switch what you're prepping on the fly, and simultaneously keep the turned off prep 'half cocked', you would conceivably always have a prep in the hand, considering all you'd have to do is always have at least one vague rune placed somewhere, and considering your character made eleven in the last two posts alone, that clearly would never be an issue for him.
To drive the point home more, let's look at this practically:
Let's say you have been prepping an attack as of your last post, but the situation demands that you switch to maturing the prep of one of your other runes to properly defend my incoming attack, thus leaving that attack 'half cocked' instead of fully prepped. Your character would be able to survive my attack, and then regain the prep lost at the very beginning of your next post, instead of having to restart it in the following post if you really wanted it that badly, meaning you'd almost always be able to do this, provided you just keep chucking runes everywhere. Any other time, you would be forced to take damage or evade (since suddenly changing what's prepping on the fly is not allowed in most other places while being able to count that action as a full prep, especially if you'd take damage logically otherwise), but instead you can just 'surprise! I have hidden preps!' At any time you don't feel like taking damage or actually dealing with something. The room for abuse here is astronomically high.
In conclusion, you either agree to T1E or you dont, and you already said you would earlier. I have no desire to do in-betweens, or rule negotiations that allow you to bypass the restrictions put in place for convenience.