Birthright: Chimaeron

Assuming Kits are currently not allowed from cross-class.

A way to simulate Dual-Classing for humans would be to allow those character who were legally able to dual-class in the base rules, to represent that by selecting a cross-class kit (a second kit as necessary)

They get the main adventure benefits/drawbacks of the kit for their 'main character sheet' (obviously a number of kits would need to be scrutinized)
The character gets the WP and NWP options available to either class
The character gets no bonus WP and NWP slots
The Character XP and advancement remains as it
Random Adventures the character counts as both classes for calculating bonus.
Random Adventure the Character gains reduced bonus for ECL item (just as a multiclass)
Does not grant bonus RP income
Does not grant cross-class abilities (Realm spells, trade chains etc)

Notes:
If this option is selected it should cost the Human Domain their Single class bonus Domain Point, possibly bonus human point as well(or instead)

My way to do it is just to have dual-class characters start over as level 1 in the new class. And that's it.

That's still a fairly potent option for human characters able and willing to take advantage of it.

The problem with dual cassing has been birmail. I referenced a possible solution in the race balance thread.

Clay was a half elf. With a human domain. He was never was able to get any elf lands or settlers.... So he ended up acting like a multi class human that had a -1 to everything... Although the long life span did allow him to keep leveling up without having to change characters.

Yeah. I intended to settle the island's mountains with my Vos settlers, but they ended up going extinct in the region instead.