Given how long even baseline elves can live, and how long it can take to cultivate the ideal bloodline, the existing succession mechanics can be quite a nuisance. I think elf dynasties would be well suited by a cultural elective succession law (much like ones that already exist), allowing you to hold an election for the next player heir where any legitimate dynasty member can be the successor (even great-great grandkids, etc).
Election conditions could suit the general theme of elven bloodline obsession. Just going to list out every idea I can think of on the spot.
- fertility is essential, the more the better
- maybe only high elves (and above) are eligible candidates
- candidates with bloodline traits could be favored
- heterosexual preferred
- electors may have some preference for their direct family, but not nearly as much as usual
- could make it so that ONLY the strongest blood is eligible, so if you have high elves no regular elves are eligible, and if you have high elves with bloodline traits, high elves without them are ineligible, etc. Potentially factor in vanilla traits like fecund, pure blood, strength, health, to generate a "blood score", to the point where it isn't even an election, and more of a dna tournament.
In general, the criteria could be made very specific so that this isn't just a convenient way to subvert vanilla succession.