You can only do so much to protect people. There comes a point when people need to stand up for themselves. If they are not willing to do that, then too bad.
And in this case, where the ruler has created a duchy, what's the big problem here? The ruler has created a new duchy that people in the realm don't like? Big deal. It's not like that's going to kill the realm. (And even if it did, it wouldn't be the first time a ruler killed their own realm.) And maybe it will cause some inner conflict in the realm, and make something happen. Because the last thing we need in the game is a system where people can just ignore their problems and they will go away all on their own. Which is what you proposed.
What I proposed was that the ruler can't just wank all over the control panel. Having just
one region as a prerequisite for a duchy won't meant too much. It would simply be a way for confirming that the ruler knows what he is doing. If King Kepler makes a duchy that can't even attract one lord why should the time be wasted and the mess be created. Sure it would piss people off, but in my opinion not in a good way. It would be kind of like "now why did you !@#$ing go and do that?" rather than "I am gravely offended, lets have a bunch of duels and referenfums etc etc": which I think is the preferable kind and I think is mainly generated spontaneously through players vying for power on a
fair battleground.I'm all for the internal strife, but not when nobles are forced to explain away dodgy game mechanics: that !@#$ just gets confusing since nobody has even ground to stand on as different people will interpret the game differently.
Also. Another thing to consider is that we need to be careful about the balance between causing debilitating internal strife vs. fun internal strife. Depending on the realm situation this can vary I understand. I think we would definitely need more opinions on the matter, but I can at least say that I can imagine (using my bm experience) an instance where a ruler would use this feature semi-abusively and the realm would not be able to stop him as according to game mechanics he has technically made a legitimate action.
Perhaps, and I assume you do, you have a different experience to mine and you think the nobles should be responsible for the ousting the ruler themselves. Maybe it has something to do with your success in Dwilight. As I have said in the past, not many people have had this success and we absoloutely should not be expected to rise to it.
I will re-iterate what I say quite a lot these days. BM should be a lightweight game. To this end the game mechanics must be set to appropriate parameters for people to play without too much stress. Greating a game mechanical mess for the players to sort out is not really doing this.