I don't agree with this planning of making the route a daily nonstop. To me, it would have made more sense to do this in a way that maximizes connections, as a fifth-freedom extension taking advantage of existing open skies agreements. Either it should have been via LOS, which would replace DL's own service to LOS from JFK, or via AMS, where one takes over one of the daily frequencies between AMS and JFK, likely DL46/7 or DL48/9. As a non-stop, 4 times weekly at most would suffice. (I'm surprised that SA runs JNB-JFK daily as a ULH nonstop.)
As for the equipment, at 6395 nmi, this would pass BNE-YVR as the longest Boeing 787-8 route in the world and is at the edge of its range.
At least other routes that seem to be outliers make sense (i.e., GYD-JFK; exists as an alternative to LY as GYD to TLV is now on a wide-body on select dates).
I also think it is too ambitious to go with a daily nonstop out of NBO. To me, it's the airline or its government trying to make a big splash while they should be focusing on what operations are not working well for them today. A 3-4x per week start would have been prudent, but time will tell of course.
In terms of your options to replace DL's LOS flight, or to fly via AMS, you are assuming that DL and KL are willing to let KQ go with it. LOS is a big money maker for DL, and KL has long kept KQ a regional partner and will not cede such coveted route. Furthermore, the JV that DL/KL have will not be receptive to KQ's ambitions. I read an article last night that alluded to the fact that DL is not [yet] placing its code on KQ's new service because of the JVs that are in place.
This might be the first big destination that KQ is going daily on, and there's a lot it's betting. Even to CDG, KQ started out gradually and had the support of AF as a feeder.
The beauty of this of course is that we will see competition to East Africa, and the mainstays such as TK, AF, KL, BA, AF, EK and ET will react with sales and possibly better offerings. One might ask if Ethiopian will look at going nonstop to IAD or even EWR now that there's direct competition.