If every title holder could assign a heir, and that nobody would have a say about it, and that nobody could be heir for more than any given title type (lordship-duchy-government), it would actually be a huge step for decentralization and, one would hope, greatly stimulate peer-to-peer interaction. Ideally it'd be a government option to tick on or off, like all the election settings currently are. As a bonus, it wouldn't necessarily induce further internal strife: while intra-realm conflict has been deemed fun for a lot of players over the years, the game also appeared to have greatly dissolved the community spirit of realms, making many aspects of the game that relied on teamwork less functionnal. With clearly-established heirs and vastly decentralized hierarchy, it'd probably be easier to both pursue self-interest without also needing a huge realm-breaking conflict to bring about power shifts, while also reinforcing local and regional allegiences.
I think the a generic heir suggestion frequently props up and is hastily shot down because of how bad it could be, usually with the thought of some form of implementation that only favors the current ruler's stability. But pre-determined successors don't have to work towards this, and it's really quite rather easy to have it concentrate power less than some current government settings are. I mean, seriously, a duke ruler of a 1-duchy realm can set ruler elections to once, and only dukes get to vote, with all positions appointed. You literally cannot concentrate power any more than this. There's some new mechanics to remove dukes I think, but even then...
I certainly wouldn't think it desireable for every realm, but having it as an option for certain realms would be nice.
