First: About Rome: if the Pope went out of his way to spam all temples don't bother. Not worth it. If it still has 2-3 empty slots, up to you, tech can be brought up quicky. And yeah, you are doing it right by holding onto only castles.
Two empty slots in Rome currently; not sure what the third slot is.
It's gonna be my capital eventually (I think I have to , don't I, to form the Roman Empire, which is sort of the objective for this playthrough to bring it into EUIV), but needs development first, then.
('Nother castle is obvious - should the last slot be a city or a third castle in this case.)
Second: look at a de jure duchy, give all counties to different counts, promote one count to duke. If you start to run ouf of vassal limit give him 2 duchies, or 3. with imperial administration you can revoke duchies for free anyway. Just take care he isn't able to form a kingdom. (more than 50% of de jure kingdom lands and 2 duchies held are the criteria)
(I'm on Charlmagne, so I can only revoke viceroyalties for free.)
You could check that your vassals aren't angry at you because you have their de-jure holdings as your vassals.
Open your character page, click vassals tab and check your relations with each duke and count. See if there are any negative modifiers for "desires barony of xyz".
I've noticed in some Byzantine starts, the emperor is liege lord of various barons and mayors throughout the empire, but the counties those baronies and mayors are in aren't owned by you, they're owned by your counts or dukes, and they're not happy about it, giving a permanent relationship negative modifier.
So... From both of the aboce, what I need to do is have a one-count-per-county policy (might need more counts...) and then promote one of the counts in that duchy to duke (well viceroyalty duke anyway) and so then all the counts in that duchy will be
his vassals and not mine? Presumably decreasing my vassal count (since they're like, his problem now) and allowing my to use said count on duchies (and kingdoms), not counties?
Presumably this then applies to the kingdom scale as well?
3) Elective. Unless I missed this in a patch, children can still be BITP. You get opinion bonus and easier time picking heir (especially if not one of your children).
I do appear to have BITP for all my children and one of the first things I did (like in 769) was switch to elective.
With elective he runs the risk of not getting the heir he wants. Why bother with it since one can basically elect the heir risk-free in primo?
The only problem with that is if your chosen heir goes down the scupper (as one did already) and your second-best choice would have been an older son, you're kinda buggered. (My eugenics program has kinda fallen apart on the basis could I buggery find and decent females and the one I did marry off to my best child candiate first produced a crap hunchaback and then never passed her Genius one to anyone...!)
If (see merchant republics thing later) I have more doges that strategos, will that impinge of my ability to pick my heirs more than currently?
Edit: Also, I can't get primo back until I get legalism 3, which I don't think I have have. So elective's gonna be it fo a while...!
Fourth: yeah you do want more, more cash is always nice. I pick them from smaller de jure kingdoms so they will be useful much much later when all my vassals are kings and they won't get declared by their de jure kings. Having Genoa would be tricky if you hand out Kingdom of Italy to someone since he will keep attacking it....
Suitable kingdoms for this (their de jure capital is on coast): Taurica, Britanny, Galicia, Wales, Denmark. Note that only 10% of your territory can be made into vassal republics, look at how many counties you have and do a quick math.
So, more doges, less strategos? (Or "as many doges as I can possibly have, everyone else Strategos or viceroyalty king")? Will that impede my ability to control my vassals more as I can't then viceroyalty them or is that countered by rebellious merchant republics being less of a hassle to deal with because of smaller levy sizes...?
(You can't have viceroyalty merchant republics, can you?)
Edit edit: Am I also correctly reading all this that one way to deal with troublesome vassals in king-over it yoink their viceroyalty sharpish like, before they can get too uppity and slap it onto someone else in their duchy so it becomes that other guy's problem?