So, to come back to this after having played a bit of my first 2.35 campaign as Saba, 84 turns in, I have a few extra house rules I use.
For one, I try to emulate "casus belli", or the cause for a war, in what I can do during a war and after its conclusion. I emulate establishing various casus belli by sending a spy to a settlement and having them stay there for a lengthy period, after which I pounce on various random events and tie them to my target. A good example of this as Saba is how the Marib damn is occasionally damaged, in combination with a minor Eleutheroi stack that appeared, I was able to pin this to the settlement and determine that the ruler there was a tyrant (he had the heartless ruler trait) and had been raiding not only my lands but also his own.
After sending a diplomat there for some time, I figured I negotiated with certain local leaders that I could justly overthrow this regime. However, the man in charge is a good defender and excellent tactician, so for the last few years we've only been able to initiate sieges but not do anything decisive. In any case, when I do finally decide to take the settlement, no doubt I'll only install a tributary state government (the precursor to allied state governments) and leave it like that for 10-20 years (so between 40-80 turns in that state). We overthrew the regime, and have exacted a tribute from the leaders we put in charge, but it wouldn't be right in all likelihood to say we are allies yet. At some point after that 10-20 year mark, I'll send a high ranking diplomat to the settlement and have him establish an embassy there by staying for a while, and then we'll be able to work to create an allied state and appoint a local leader. I also don't let myself build any buildings or recruit in provinces without a governor, so this local leader is essential to me actually ever doing anything with the province. God help me that I got a dull, uncharismatic, languorous leader in one of my allied settlements, as for sure he won't build anything, or very rarely if he becomes an attuned governor.