And, for posterity, let it be known:
This method of changing government type works.
Especially with the rulership established by a vote instead of by random claiming. In a one-duchy realm where the ruler is the duke, the ruler can change the government system basically at will (change ruler voting to dukes only, step down, wait for anarchy, run for office, vote for self, win, change government).
With multiple duchies or less concentrated power it'd be trickier.
Be aware that once the proper anarchy vote is committed (it's implemented, I just didn't want to screw things up for you further by committing it while you were still working out the government), the anarchy ruler election will be among all nobles in the capital. Whoever is in the capital (and part of the realm) will be eligible to run, and eligible to vote. Leaving the capital will drop your name out of the running and cancel your votes.
So you won't have complete control even if you originally set the voting to Dukes-only.
