I sent an email to Waze asking that they effect the closure of sections of I-5 in the Vancouver/Salmon Creek area coming up on the weekend of June 7.
A bit late for this particular closure, but it looks like Waze will be rolling out “events” soon to make this kind of road closure reporting easy for everyone! http://www.waze.com/blog/how-to-beat-epic-traffic-caused-by-summer-events/
In fact, Waze did handle this closure exactly as described after I submitted it using the process they will be rolling out to everyone. It just didn’t get published on the events website, but the closure icons and red/white banded closed sections of I-5 did just like they were supposed to. 
Here’s how this closure looked in livemap over the weekend.
We have another closure LIKE this which has begun as of this evening and will run until 5 AM Monday…
DRIVER ALERT, WEEKEND CLOSURE: Friday, July 12 until Monday, July 15 - All lanes of northbound I-405 between Southeast 8th Street and SR 520 will close from 8 p.m. Friday until 5 a.m. Monday to allow crews to replace concrete panels. The Southeast 8th Street HOV on-ramp to northbound I-405 will also close for the weekend. Detours will guide drivers around the closure. (Reminder, SR 520 between Montlake and I-405 is also closed.)
So…I used a fake GPS signal to move to points on these segments where a driver might enter the freeway, and closed the next segment ON the freeway. Doing this about 7 times put the closures in the right places on my own phone, but…what will it now take for it to actually start rerouting people and show up on the map? Is there any way to do it?
These have to be scheduled. Waze won’t process this until Sunday morning, so they could get it in for one of the days at least.