The plot thickens…
Your code generated the lines no problem, but they could not be used for rooms, as previously stated. Also, you cannot change their LevelId, even though it is right there in RevitLookup. That parameter isn’t available, apparently. You said as much here.
But yet, I am able to create room lines using a DynamoMEP node:
Notice that I am using straight-up, 1:1, flattened lists of Dynamo curves and respective views.
The C# code is here.
How simonmoreau did it, I am still trying to figure out, but one of the comments is interesting:
// PB: This implementation borrows the somewhat risky notions from the original Dynamo
// implementation. In short, it has the ability to infer a sketch plane,
// which might also mean deleting the original one.
Risky, huh? Bring it!
RoomLinesTest.dyn (3 MB)