Now that week 2 is in I made the projection for the Demiurge Contract event. You can actually fully 6* her from zero if you buy ether which is great. Compared to last time you get 2x from missions (5->10) and 5x from ether (3->15) which is very good.
There is some uncertainty still due to when exactly does it end (says before maintenance on 10/23), if check-in ends at day 21, and if week 3 will award same rewards as week 2.
Conclusions so far:
From zero/3* you can safely 6* her (900 pieces) by buying with ether for 20-21 days.
If you got hit by the arena bug in day 1 (-4 pieces) then you need to buy 21-22 days.
For people that already had the hero (extra 150 pieces) or missed some days, check the table and calculate accordingly.
Total ether cost for 20 days is 6000, not bad at all for a maxed Demiurge.
Outerrise.