From the Regent Guide (p. 42, table 3-2):
Designation 1RP/province or holding level bequeathed (at the moment of the ceremony) Willing regent designates another scion as his heir; that scion will automatically be crowned when the old regent dies.
So, to use WIT as an example, as I have 83 holding levels in total it would cost me 83 RP to designate an heir to my domain? Is there some reasoning behind the fairly steep cost? I understand that designating an heir is no light matter, as it solves several problems that usually occur upon a regents death, but requiring to spend a full 3-4 turns of not spending RP at all (depending on BS and domain size) to save up RP seems rather steep to me.
Is there any way the rules can be tweaked? It has been somewhat of a mantra for the DM (at least towards me) to make sure to have a designated heir to avoid troubles, all throughout the game, but the rules seem unneccesarily preventive of this. Cutting the cost to for instance half of todays cost (exact number is up for debate) would be a simple fix that would ensure that the cost is still high, but not so that players inclined to use such an action can never hope to afford it.
Edit: As Marco pointed out, might be smart to refer to the correct action in the Regent guide.